Welding Amp Chart: Amperage Settings for Stick, MIG & TIG

A new welder once spent an entire afternoon fighting 1/8-inch steel plate, blowing holes through it and blaming the cheap rod. The machine dial was set almost 50 amps too high — one glance at an amperage chart would have fixed the problem in ten seconds. That is the quiet power of a welding amp chart: it turns guesswork into a starting point you can trust.

What a Welding Amp Chart Is and Why Every Welder Needs One

A new welder once spent an afternoon fighting 1/8-inch steel plate. He blew holes through it, undercut the edges, stuck the rod a dozen times, and finally blamed the cheap electrode. The machine dial, it turned out, was set almost 50 amps too high. One glance at an amperage chart would have fixed the problem in ten seconds.

That is the quiet power of a welding amp chart: it turns guesswork into a starting point you can trust, then gets out of your way.

So what exactly is a welding amp chart?

At its core, a welding amp chart is a reference table that matches a job to a recommended starting amperage. Most charts cross-reference four variables at once:

• Process — SMAW (stick), GMAW (MIG), or GTAW (TIG).
• Base metal type and thickness — mild steel, stainless, aluminum, and so on, measured in gauge, inches, or millimeters.
• Joint type and position — butt joint, lap, outside corner, fillet, welded flat or overhead.
• Electrode or wire diameter — a 1/8-inch 7018 rod, 0.030-inch MIG wire, a 3/32-inch tungsten, and the rest.

Feed a chart those four inputs and it hands back a number, often somewhere around 110 to 130 amps. That number is where you set the dial before you strike the first arc.

Amperage in plain language

Amperage is the amount of electrical current flowing through the welding circuit — think of it as the volume of electricity. More current means a hotter arc, deeper penetration, and more metal deposited per second. Less current means a cooler, shallower, more controllable weld.

A reliable rule of thumb for steel gets you close: roughly 1 amp of current per 0.001 inch (0.025 mm) of material thickness. A 1/4-inch plate therefore suggests about 250 amps in the flat position, while 16-gauge sheet (roughly 0.060 inch) suggests around 60 amps. It is an anchor, not gospel.

Why does one variable deserve that much attention? Because heat is the single most controllable variable in arc welding. Travel speed, arc length, and technique all matter, but amperage is the dial that decides whether you burn through the plate or leave it cold and unfused. Voltage, electrode angle, and gas flow refine the result; amps decide whether a weld is possible at all.

What the chart can and cannot tell you

Here is where welders get into trouble. A chart tells you where to begin, not where to finish. It cannot account for:

• Your specific machine’s calibration, which may read hot or cold compared to the display.
• Heat-sinking fixtures, position work, or open roots that pull heat away from the joint.
• Mill scale, rust, oil, or paint on the surface.
• Ambient temperature, wind, and outdoor conditions.
• Personal technique — arc length, travel speed, and electrode angle.

That last point matters more than it sounds. If your procedure documents specify a range, that range wins — full stop. Generic charts are published for average equipment under average conditions, and structural codes such as AWS D1.1 require work to follow qualified procedures rather than a shop’s wall poster. Equipment setup carries regulatory weight too: OSHA standard 1910.254 requires welding machine conductors and equipment to be rated and installed for the machine’s actual loading conditions — one more reason to know what amps you are really running.

Why every welder keeps one handy

Beginners use charts to avoid burning through material on day one. Experienced welders keep them as a sanity check whenever they step into an unfamiliar process, thickness, or alloy. Moving from steel to aluminum shifts the settings significantly, so having a reference for Aluminum MIG Welding: The Complete Practical Guide saves a lot of scrap metal. The same applies when you pick up a rod you have never run before, such as one of the options in our All Position Welding Rod Guide: Types, Uses & Tips.

What this article will cover

In the sections ahead, we will work through the whole topic in order:

1. The physics behind the number — what amperage actually does in the arc, and how it differs from voltage.
2. How to read any chart, including a worked example for 1/4-inch mild steel.
3. Standalone amp charts for stick, MIG, and TIG, with rod and wire sizing.
4. Settings by metal type — steel, stainless, aluminum, and cast iron.
5. The classic mistakes, with a symptom-to-fix troubleshooting table.
6. Heat input, duty cycle, and safety limits that sit above any chart.
7. A condensed quick-reference card you can tape to your machine.

By the end, you will be able to walk up to any machine, size the joint, and pick a number within a few seconds, then refine it by watching the puddle. Adjust by 5–10 amps at a time, and let the code and the procedure override everything else.

How Welding Amperage Actually Works: The Physics Behind the Number

A chart is only useful if you understand what the numbers on it actually control. In arc welding, amperage is the one variable you set directly that decides how much heat the arc dumps into the metal, so it pays to know what is physically happening when you turn the dial.

What Amperage Does in the Arc

Amperage is simply the rate of electron flow across the arc — how many electrons pass a given point each second. As those electrons strike the workpiece and travel through the arc column, they run into electrical resistance, and resistance converts electrical energy into heat. This is the same principle as a toaster element, only far more concentrated: heat generated rises with the square of the current, which is why a 30-amp increase does far more than “a little” extra melting.

Because of that, amperage is the primary throttle for three things:

• Penetration — how deep the fusion zone reaches into the base metal.
• Deposition rate — how quickly the electrode or wire melts and piles into the joint.
• Puddle fluidity — a hotter puddle wets out and ties into the sidewalls; a cooler one sits up and refuses to fuse.

Voltage does related but different work. In most processes it governs arc length, and arc length shapes the bead: more voltage gives a wider, flatter profile and a longer arc; less voltage gives a narrow, penetrating arc. In plain terms, amperage melts, voltage shapes. Travel speed is the third partner, deciding how long that heat stays over any given inch of joint.

Why Thicker Metal Needs More Current (and Why Aluminum Is Different)

Thicker sections act as heat sinks. The heat entering the joint spreads sideways and downward through a larger cross-section, so the arc has to supply more energy just to bring the fusion zone up to temperature before it moves on. Doubling thickness does not double the required amps, but the trend in every chart is unmistakably upward.

Aluminum breaks the pattern. It conducts heat roughly three times better than steel, so it pulls heat away from the arc almost as fast as you put it in. At the same time it melts at about 660°C (1,220°F) compared with roughly 1,500°C (2,730°F) for steel, meaning there is a narrow window between “not flowing” and “collapsed.” The practical result is that aluminum often needs more current than steel of the same thickness, plus quick pedal response — see Aluminum MIG Welding: The Complete Practical Guide for how those settings play out on the machine.

Heat Input: Where Amps, Volts and Speed Meet

That formula is the reason two welds made at identical amperage can look nothing alike. Slow the travel speed and you deliver more joules to every inch of the joint, even though the dial never moved. Heat input is the honest measure of what the metal experienced, and it is the basis for the arc-energy limits written into structural codes. AWS D1.1, the Structural Welding Code–Steel, requires welding procedures to define and record the parameters that produce acceptable properties — excessive heat input causes grain growth and toughness loss, so procedures cap it.

Constant Current vs Constant Voltage: Who Actually Sets the Amps

Machine type determines which knob really controls the heat. Stick and TIG power sources are almost always constant-current (CC): the machine holds the amperage you dial in, and voltage rises or falls with arc length. That is why a TIG operator can modulate heat with a pedal while the current stays put. Constant-voltage (CV) machines — the norm for MIG — hold voltage steady instead, and the resulting current is set by wire feed speed: push more wire in, the arc responds by drawing more amps. Miller’s parameter guidance is built around this relationship, where wire size and feed rate are the practical entry point rather than an amps dial. Even in demanding applications like Aerospace TIG Welding, the same physics applies; only the tolerances shrink.

Keep those two models straight and the charts in the next sections make immediate sense: stick and TIG charts give you an amperage range directly, while MIG charts translate wire feed speed into the current you are actually running.

How to Read a Welding Amp Chart: The Five Inputs You Must Know

An amp chart matches inputs to a number. Hand it the wrong inputs and it will confidently hand you the wrong setting. Reading one properly takes about ninety seconds once you know the five things every chart is asking for.

Input 1: Identify the Process

First, confirm which chart you are holding. Stick (SMAW), MIG (GMAW) and TIG (GTAW) each put heat into metal differently, so a stick chart has no business setting your TIG machine. Transfer mode matters too: short-circuit MIG and spray MIG on the same wire are effectively different animals. If you run a multi-process unit, make sure you are reading the page for the mode you actually selected on the front panel.

Input 2: Identify the Base Metal and Its Alloy

Steel, stainless and aluminum are not interchangeable rows. Mild steel is the baseline everything else is measured against. Stainless holds heat and typically wants less current, while aluminum conducts heat away so fast that it wants significantly more. The alloy matters as well: a 5356 filler behaves differently from 4043, and coated or galvanized stock changes the picture again. Surface condition counts too, which is why prep matters as much as the dial setting — see Aluminum Cleaner for Welding: How to Prep Aluminum Right for what that looks like on aluminum.

Input 3: Measure Thickness Accurately

This is where most beginners lose the plot. Never eyeball thickness. Use a caliper or a sheet-metal gauge, because an off-by-one-gauge mistake is one of the top causes of burn-through. The error is not linear either: thinner sheet metal needs disproportionately less current, since there is less material to sink the heat. Twenty-gauge sheet commonly sits in the 30–60 amp band, while a jump to 16 gauge can mean doubling the setting. Working in metric? Convert before you read the chart rather than after — mixing inches and millimeters mid-row is an easy way to land in the wrong band.

Input 4: Joint Type, Position and Number of Passes

Charts assume a flat butt joint unless they say otherwise. Change the geometry and you change the answer:

• Out-of-position work: vertical-up and overhead generally need about 10–15% less current than flat, so the puddle does not sag or drip on you.
• Open-root joints: less heat than a closed butt joint of the same thickness, because there is nothing behind the arc to absorb and reflect the energy.
• Lap and outside-corner joints: usually at the lower end of the band, since one edge is thin and unsupported.
• Multi-pass fills: the root pass often runs cooler than the cap, where you are welding into a preheated, heavier section.

If vertical and overhead settings confuse you, the All Position Welding Rod Guide breaks down which electrodes tolerate which positions.

Input 5: Electrode or Wire Diameter

Finally, pick the filler size. A 1/8-inch 7018 and a 3/32-inch 7018 occupy different amp bands for the same plate, and rod size works together with thickness — you would not run a 1/8-inch rod on 20-gauge sheet even though a chart might technically list an overlap. For reference ranges by electrode class, Lincoln Electric’s AWS classification guide explains what those three-digit codes actually mean.

Worked Example: 1/4-Inch Mild Steel, Flat Butt Joint, 7018

Work the steps in order:

1. Process: stick/SMAW.
2. Base metal: mild steel, clean and mill-scaled.
3. Thickness: measured at 1/4 inch (6.4 mm) with a caliper.
4. Joint: flat butt, closed root, single or multi-pass.
5. Filler: 1/8-inch E7018.

Using the common rule of roughly one amp per 0.001 inch for steel, 0.250 inch points to about 250 amps as a theoretical ceiling — which is exactly why 1/4-inch plate typically appears in a 175–250 amp band depending on position and joint. Since this is flat and closed, start in the lower third of that band, around 180–190 amps, then adjust. Hobart Brothers’ 7018 amperage guidance reinforces starting low and tuning upward rather than dialing to the printed maximum.

When to Abandon the Chart

Skip the chart when the job already has a qualified procedure. If you are working to a WPS under AWS D1.1, the procedure’s essential variables override any generic table. The same goes for short-circuit MIG settings published by the machine’s maker — Miller’s parameter guide is the better authority for that machine and wire. Charts also assume clean, dry, mill-scale-free metal. Rust, paint, oil, damp electrodes and long, voltage-dropping cable runs all shift the real amperage at the arc. When the puddle contradicts the chart, trust the puddle — and log what worked so your next reference is better than the last.

Stick Welding (SMAW) Amp Chart: Rod Sizes and Starting Ranges

If stick welding has one golden rule, it is this: the diameter of the rod in your stinger is the biggest decision you make before you strike an arc. Amperage follows rod size more closely than any other variable. A 1/16-inch electrode cannot dump current into a puddle the way a 3/16-inch rod can, and the manufacturer ranges published for each size exist for a reason. Know your rod, and the machine dial is already narrowed to a small window.

Why Rod Size Drives Amperage

Current flows through the electrode into the arc, and the rod’s cross-sectional area sets how much it can carry before the core wire overheats or the arc turns unstable. Thin rods run at low current and only make sense on thin material; large rods need hundreds of amps and would vaporize sheet metal instantly. As a working guide, a 1/16-inch rod tops out near 40 amps for sheet work, 1/8-inch rods live in the 90–150 amp zone for most mild steel electrodes, and 3/16-inch rods can require well over 200.

Stick Amp Chart by Electrode and Diameter

The table below lists typical published starting ranges for the four electrodes most often found in a shop. Treat them as starting bands, not fixed values, because manufacturer electrode charts vary in how they round and phrase their recommendations.

Electrode	Diameter	Typical Thickness	Starting Amps (flat)
6010 / 6011	1/8 in (3.2 mm)	1/8–3/16 in	90–130
6010 / 6011	5/32 in (4.0 mm)	3/16–1/4 in	135–180
6010 / 6011	3/16 in (4.8 mm)	1/4–3/8 in	200–275
6013	1/16 in (1.6 mm)	20–18 gauge sheet	20–40
6013	1/8 in (3.2 mm)	1/8–3/16 in	80–120
6013	5/32 in (4.0 mm)	3/16–1/4 in	130–170
7018	1/16 in (1.6 mm)	18–16 gauge sheet	20–40
7018	1/8 in (3.2 mm)	1/8–3/16 in	100–150
7018	5/32 in (4.0 mm)	3/16–1/4 in	130–190
7018	3/16 in (4.8 mm)	1/4–3/8 in	200–280
7024	1/8 in (3.2 mm)	1/8–3/16 in	110–160
7024	5/32 in (4.0 mm)	3/16–1/4 in	150–220
7024	3/16 in (4.8 mm)	1/4–3/8 in	200–275

Polarity: DCEP, DCEN and AC

The same rod at the same amps behaves differently depending on which way the current flows. On DCEP (electrode positive), roughly two-thirds of the arc heat concentrates at the electrode, giving deeper penetration and a stable arc. On DCEN (electrode negative), heat pushes into the workpiece and the rod melts faster, producing a shallower, wider weld that suits thin material. AC alternates direction many times per second; it is common on older and budget machines and handles general repair adequately, but it gives up some of the penetration consistency of DCEP. The classification itself, such as E7018, is codified by AWS electrode classification standards, and the final digit indicates which coating is designed for which polarity.

Cellulosic Versus Low-Hydrogen Coatings

Coatings explain much of that behavioral difference. The 6010 and 6011 family uses a cellulosic coating that burns fast, digs deep and freezes the puddle quickly, which is why they are the classic root-pass and out-of-position rods. The trade-off is more spatter, a rougher bead and higher hydrogen in the arc. Low-hydrogen 7018 rods run smoother, lay a flatter bead with better impact resistance, and must be kept dry: rods left out overnight pick up moisture and lose their low-hydrogen rating. The 7024 carries a heavy iron-powder coating built for high deposition in flat and horizontal work, where it out-deposits anything else in the box. This is also where 7018 amperage guidance becomes especially useful, since the rod’s buttery arc can hide settings that are slightly off.

How to Tune Inside the Range

Once you have the band, do not start at the top. Set the dial in the lower third, strike an arc on scrap of the same thickness, and adjust in 5–10 amp steps. Move up if the rod feels sluggish or the bead stands proud; move down if the arc sounds loose, the puddle wanders or the edges melt away. Position matters too: overhead and vertical-up work generally needs 10–15 percent less current than flat, because gravity is already pulling the puddle where you do not want it.

That symptom loop is the same logic behind the strengths that keep SMAW on job sites: a simple machine, one variable at a time, and a bead that tells you exactly what to change next.

MIG Welding (GMAW) Amp Chart: Wire Feed Speed, Voltage and Thickness

If you stand in front of a MIG machine looking for the amperage dial, you mostly will not find one. Most MIG welders give you two controls: wire feed speed and voltage. That trips up beginners constantly, because in MIG welding the wire feed speed is your amperage control. Push more wire into the arc per minute and the arc has to melt more metal per second, so current rises. Voltage, meanwhile, controls how the arc behaves once that current is flowing: arc length, bead width, spatter level and how flat the puddle spreads.

This relationship matters when reading a welding amp chart, because a MIG chart usually lists wire feed speed in inches per minute (ipm) alongside amps. The two numbers are two views of the same setting.

Why Wire Diameter Sets Your Range

Thinner wire carries higher current density, so a small-diameter wire can run spray-like arc characteristics at amps where a thicker wire would just short-circuit. In practice:

• 0.023-inch wire is generally for sheet metal around 22–24 gauge, especially on thin automotive panels where heat control is everything.
• 0.030-inch wire covers the broadest range of light fabrication, roughly 24 gauge up to 3/16 inch.
• 0.035-inch wire is the common choice for 1/8-inch and heavier steel, though it can run thinner material at reduced settings.

MIG Amp Chart by Material Thickness

The table below gives starting settings for solid ER70S-6 wire on mild steel in the flat position. Treat every number as a starting band, not a destination.

Material thickness	Wire diameter	Approx. amps	Wire feed speed (ipm)	Voltage (approx.)
22–24 gauge (0.025–0.030 in)	0.023 in	35–55	150–250	14–16 V
18–20 gauge (0.040–0.048 in)	0.023 / 0.030 in	55–85	250–350	16–18 V
1/8 in (0.125 in)	0.030 / 0.035 in	110–135	350–450	18–20 V
3/16 in (0.187 in)	0.035 in	140–175	450–550	20–22 V
1/4 in (0.250 in)	0.035 in	175–210	550–650	22–25 V
3/8 in	0.035 / 0.045 in	210–260	650–750	24–28 V

Wire feed speeds vary between brands and machines, so trust the amps and voltage more than the exact ipm number on your feed roll.

When No Chart Is Available: The Miller Formula

Miller’s published guidance offers a reliable fallback: set wire feed speed using the wire size formula, then apply the 1 amp per 0.001-inch rule for material thickness. Welding a 1/4-inch (0.250-inch) plate implies roughly 250 amps as an upper-target check; dialed back for joints and positions, that lands you near the 175–210 amp band above. The rule works because penetration demand scales directly with thickness, as Miller’s parameter-setting guide explains. Note the formula gives a ceiling to sanity-check against, not a setting to blindly dial in on a lap joint in the vertical position.

Gas Choices and Transfer Modes

Shielding gas changes how your amps behave:

• 75/25 argon-CO2 is the general-purpose standard for mild steel: stable arcs, moderate penetration, low spatter.
• 100% CO2 costs less and digs deeper, but produces more spatter and a rougher arc at low amps.
• 100% argon is the go-to for aluminum MIG, paired with 4043 or 5356 filler wire. Aluminum prep and technique deserve their own attention, as covered in Aluminum MIG Welding: The Complete Practical Guide.

Short-circuit transfer runs cooler and is forgiving on thin, gap-prone joints. Spray transfer puts heat in efficiently on thicker steel, giving flatter, faster beads with minimal spatter once your amps reach the 180–200 amp threshold on argon-rich gas.

Flux-Cored Wire Needs More Current

Flux-cored arc welding (FCAW) generally runs 10–15% higher in current than the equivalent solid wire to reach the same penetration, because part of the wire’s cross section is flux rather than steel. So a setting that works at 180 amps with 0.035-inch solid ER70S-6 may need roughly 200–207 amps with a 0.035-inch flux-cored wire on the same joint. Wire chemistry also shifts settings, which is why electrode selection charts like Alloy Steel Welding Electrodes: Selection, Use & Safety are worth reading before switching filler types.

For aluminum specifically, remember that aluminum’s high thermal conductivity pulls heat away from the puddle faster than steel does, so your real adjustment may be speed and preheat rather than the amp number itself. Cleaning matters more too; a fresh, oxide-free surface is the difference between a clean bead and a porous mess, which is why proper prep with the right Aluminum Cleaner for Welding comes before the settings conversation.

Start inside the middle of your chart’s range, dial in on scrap, and let the puddle tell you whether to move up or down.

TIG Welding (GTAW) Amp Chart: The 1 Amp per .001 Inch Rule

Of the three processes in this article, TIG is the one that runs on a rule instead of a vibe. Stick and MIG charts give you a band and tell you to read the puddle. TIG gives you a formula, and most tungsten operators can recite it in a sentence: one amp for every one-thousandth inch of material thickness. That is why a published TIG amperage chart looks so tidy compared with the others — the numbers reflect predictable physics rather than a consumable coating fighting you.

The Baseline Rule for Steel

On a flat butt joint in mild steel, clean metal, no fixture clamping it down and a normal arc length, set the machine to 1 amp per 0.001 inch. Run the math: 125 amps for 1/8-inch plate, about 190 amps for 3/16-inch, and roughly 250 amps for 1/4-inch. Those are starting points for a pedal, not fixed settings — you typically begin below the top of that number and modulate as the puddle develops.

Thickness	Mild steel (butt joint)	Aluminum (butt joint)	Suggested tungsten
0.063 in / 1.6 mm (16 ga)	60–70 A	40–60 A	3/32 in (2.4 mm)
0.090 in / 2.3 mm	90–110 A	55–80 A	3/32 in (2.4 mm)
0.125 in / 3.2 mm (1/8 in)	110–130 A	80–110 A	3/32–1/8 in
0.187 in / 4.8 mm (3/16 in)	160–190 A	110–140 A	1/8 in (3.2 mm)
0.250 in / 6.0 mm (1/4 in)	230–250 A	140–160 A	1/8 in (3.2 mm) or larger

The aluminum column is where the rule gets its famous modifier: add roughly 20–25 percent more amperage than the steel number. Aluminum isn’t stubborn because it melts lower — it’s stubborn because it conducts heat away from the arc so fast that you spend most of your energy warming a patch of plate the size of a half-dollar before anything will wet out. The extra current gets the puddle started; once it forms, you back off. Generic TIG calculators build this bump right into their output.

Adjustments That Move the Number

The formula assumes a plain butt joint on a bench. Real joints push the setting up or down:

• Lap joints and outside corners: back off 10–15 percent. Two edges meeting at a corner have almost no mass behind them, and the amps that welded a butt will melt the edge away.
• Open-root joints: run cooler. There is no backing behind the keyhole, so excess current blows the root through before you can bridge it.
• Heat-sinking fixtures: add current. A heavy copper backup bar or a part clamped to a steel table steals heat, sometimes enough that you need another 10–20 amps to keep the puddle moving.
• Out-of-position work: gravity works against the puddle, so reduce amperage rather than fighting the sag.
• Mill scale, oil or a poor argon blanket: the arc works harder. Clean the metal first — prep matters more here than anywhere else, which is why Aluminum Cleaner for Welding: How to Prep Aluminum Right is worth reading before you blame your settings.

Tungsten Size and the Amperage Band

Tungsten diameter is chosen backwards from the current. Published guides pair a 3/32-inch tungsten with roughly the 40–150 amp range, which covers most light fabrication and bodywork. Move to 1/8-inch tungsten once you are consistently above about 100–120 amps, because a thin electrode will ball, taper to a nub and contaminate the puddle under sustained high current. Below 40 amps, drop to a 1/16-inch or 0.040-inch thoriated or lanthanated tip so the arc starts cleanly instead of wandering. For AC aluminum, use a dedicated AC blend (zirconiated or a modern lanthanated) with a slight balled or truncated point; for DC steel and stainless, a pointed lanthanated or ceriated electrode covers almost everything.

Pedal Control, Downslope and Post-Flow

The chart value is really your maximum available current. With a foot pedal you strike the arc at perhaps 60–70 percent of it, let the puddle reach full width, then hold steady. Machines with downslope let you program a ramp that reduces current at the end of the bead so the crater fills instead of cracking — critical on aluminum, which is notorious for crater cracks. Post-flow keeps argon over the hot crater and the tungsten for a few seconds after the arc stops, preventing oxidation and electrode damage.

The best way to internalize all of this is repetition: weld a plate, note the thickness, joint and exact amps in a log, and compare it against your next attempt. Practitioners working to tighter standards, such as Aerospace TIG Welding: Standards, Techniques, and Training, treat that record as part of the procedure rather than optional note-taking. The chart gets you close in ten seconds; the logbook gets you repeatable.

Amp Charts by Metal Type: Steel, Stainless, Aluminum and Cast Iron

Most generic amp charts are built on one quiet assumption: the base metal is plain mild steel, clean, flat and sitting on a bench. That covers a lot of shop work, but switch to stainless, aluminum or cast iron and the same 1/4-inch plate no longer wants the same number. Thickness sets the ballpark; the alloy decides where in it you actually land.

Mild Steel: The Baseline Every Chart Assumes

Carbon steel is forgiving and predictable, which is why it becomes the reference point. Its conductivity, melting behavior and oxide layer are all moderate, so a thickness-based chart lands you close on the first try. For stick work, a 1/8-inch plate with a 6011 or 7018 rod sits around 90–110 amps; for TIG, the familiar “one amp per .001 inch” rule starts you near 80–100 amps on a butt joint. Mill scale and rust are the wild cards; we will come back to them.

Stainless Steel: Dial Back 10–20%

Stainless generally needs about 10–20% less amperage than carbon steel of the same thickness. The reason is thermal: stainless conducts heat less readily than mild steel, so heat stays concentrated in the joint instead of racing away into the plate. Too much current keeps the puddle molten far too long, which invites warping, heavy oxidation (“sugaring” on an unpurged backside) and, in the 300-series grades, carbide precipitation, where chromium carbides form along grain boundaries whenever the metal lingers in the 800–1,500°F range and destroy corrosion resistance. Practical fixes: lower amps, faster travel, stringers rather than wide weaves, and controlled interpass temperature. Filler follows the same logic, and AWS filler metal classifications spell out which wire or rod pairs with which alloy.

Aluminum: Push Harder, Move Faster

Aluminum runs the other way: TIG work commonly runs 20–25% hotter than steel of equal thickness, and the reason is stubborn. The oxide skin on aluminum doesn’t melt until roughly 2,070°C (3,760°F), while the metal itself goes liquid near 660°C (1,220°F). Extra current breaks that oxide layer so the puddle can wet the base metal, but the heat then spreads fast through the plate, so you compensate with quicker travel rather than lingering. Cleaning matters more here than on any other metal — see Aluminum Cleaner for Welding: How to Prep Aluminum Right for the degreasing and brushing routine. Feeding wire instead? Aluminum MIG Welding: The Complete Practical Guide covers transfer mode and gas setup in depth.

Cast Iron and Nickel Alloys

Cast iron is not a “turn it up” metal. It is welded with short, controlled beads — typically one to two inches, skipping around the joint — with preheat in the 500–1,200°F range depending on section mass, slow cooling afterward, and often peening to relieve shrinkage. Because grey iron’s graphite structure makes arc starts erratic, most welders run on the cool side of a mild-steel chart and let the preheat do the work, using high-nickel or nickel-iron electrodes.

Nickel alloys (Inconel, Monel, Alloy 20) sit between stainless and cast iron in temperament: lower current than steel, tight heat control, no long dwell. Read the procedure before the arc is struck: Alloy 20 Welding: Procedures, Filler Metals, and Best Practices is a good starting point, and Alloy Steel Welding Electrodes: Selection, Use & Safety covers how alloying elements shift hardenability and rod choice.

Thickness (in / mm)	Mild steel (TIG)	Stainless (TIG)	Aluminum (TIG, AC)
16 ga / 1.5	55–70 A	45–60 A	70–90 A
1/8 / 3.2	75–100 A	65–85 A	100–125 A
3/16 / 4.8	110–130 A	90–115 A	135–165 A
1/4 / 6.4	130–160 A	110–140 A	165–200 A
3/8 / 9.5	175–210 A	145–185 A	215–260 A

Mill Scale, Coatings and Other Curveballs

Surface condition moves the effective setting as much as a change of alloy does. Mill scale is semi-insulative and makes the arc wander; rust adds moisture and porosity; primers burn and off-gas; and zinc coatings vaporize into ugly, porous weld metal. Strip coatings at least one inch back from the joint on both sides before striking an arc, and grind mill scale to bright metal when the joint is structural. These are the conditions that make a chart look wrong when it is actually right: published numbers assume clean, dry, uncontaminated material, as Miller’s parameter guidance emphasizes.

For structural work on carbon steel, remember that a shop chart never outranks the qualified procedure: AWS D1.1 and the project’s WPS define the accepted range, and everything here is only a way to get close fast.

Common Amp Chart Mistakes and How to Troubleshoot Bad Settings

A chart can be perfect and still produce a bad weld, because the number only works when the setup around it is right. Most rods, wires and machines that get blamed for ugly beads are innocent. Nearly every failed weld traces back to two failure modes — too much current and too little — or to a handful of habits that quietly invalidate the chart you are reading.

Too Much Amperage: How to Spot It

Excessive current gives you a bead that is wide, flat and discolored, with the puddle boiling instead of flowing. Spatter is heavy, the arc sounds harsh and crackly, and thin edges melt away before you can chase them. Hang in one spot too long and you will blow clean through the joint. On stainless steel the backside turns chalky and rough — the condition welders call sugaring — because the heat held the metal in the range where chromium grabs oxygen from the shielding gas. The fix is almost never a new consumable: drop the setting, move faster, and stop weaving wider than the puddle.

Too Little Amperage: How to Spot It

The classic cold bead is tall, narrow and ropey, sitting proud on the surface rather than wetting into the toes. You get cold lap where the filler rolls over the base metal without fusing, and if your travel speed is also too fast, the arc gouges a groove the metal never fills, which shows up as undercut along the toe. Stubbing is the giveaway signature of amperage too low for the electrode diameter in your hand: the rod sticks, the arc goes out, and you spend more time chipping than welding.

Symptom	Likely Cause	Fix
Wide, flat, discolored bead with heavy spatter	Amperage too high or travel too slow	Back off 5–10 amps and speed up
Burn-through or holes on thin stock	Too much heat input, dwell in one spot	Drop 10–15 amps, shorten the arc, keep moving
Chalky, rough backside on stainless	Excessive heat, no trailing shield or purge	Lower amps, increase speed, purge the root
Tall, ropey bead sitting on the surface	Insufficient current or travel too fast	Add 5–10 amps or slow down
Cold lap and lack of fusion at the toes	Too cold, dirty or scaled surface, wrong angle	Raise amps, clean the joint, flatten the angle
Arc stubbing and hard starts	Too low for the rod size, wrong polarity	Increase 10–15 amps and check the terminals

Mistakes That Have Nothing to Do With the Number

1. Wrong wire or electrode size for the thickness. A 0.035-inch wire on 20-gauge sheet fights you with an unstable arc long before the voltage setting is to blame. Match the consumable to the thickness first.
2. Ignoring position. Overhead and vertical-up welding need roughly 10–15% less current than flat, because gravity works against the puddle. Our All Position Welding Rod Guide covers which rods are built for it.
3. Dialing to the top of the range. A chart band gives you a starting point inside the range, not a target at its ceiling. Start in the middle or lower third.
4. Forgetting that charts assume clean, dry metal. Mill scale, rust, oil, paint and galvanizing all change the heat you actually need. Prepping matters as much as dialing, which is why Aluminum Cleaner for Welding: How to Prep Aluminum Right is worth a read before you touch aluminum.
5. Assuming one chart works across processes. Stick, MIG and flux-cored settings are not interchangeable, and flux-cored wire generally needs about 10–15% more current than a solid wire of the same diameter. Even within one process, transfer mode changes the math — see Aluminum MIG Welding: The Complete Practical Guide for how differently aluminum behaves under MIG than steel.

Five Steps to Dial In Any Setting on Scrap

1. Cut matching scrap. Use the same alloy, thickness and joint type you are about to weld — test coupons from a different thickness teach you nothing.
2. Clean it. Remove scale, oil and coatings so the arc sees bare metal.
3. Set the middle of the range. Consult the chart, then set the midpoint rather than the top. Miller’s guide to setting correct MIG parameters is a solid reference for the wire-speed-to-amperage relationship.
4. Run a two-inch bead and watch the puddle. Read it against the symptoms table above before touching anything else.
5. Adjust in 5–10 amp increments and log what worked. One variable at a time. Published ranges such as the 7018 rod amperage guidance from Hobart Brothers or a standard electrode amperage chart get you close; your scrap bead gets you dialed in.

Keep that written record. Six months later, when you face the same 1/8-inch plate that started this conversation, your own notes will beat any generic table on the wall — and the rod will stop taking the blame.

Beyond the Chart: Heat Input, Duty Cycle, Safety and Code Limits

An amp chart gets the arc started, but the dial you set is only one variable in a much larger system. The same 140 amps can produce a strong, properly penetrated weld on one joint and a distorted, brittle one on the next. What separates the two is everything around the number: travel speed, voltage, machine limits, interpass temperature, and the codes that decide whether a weld is acceptable at all.

Heat Input: Why the Same Amps Can Make Different Welds

Amperage, voltage and travel speed combine into a single value welders call heat input. In US customary units, the arc-energy relationship recognized in AWS D1.1 procedure requirements is:

Codes cap heat input because excessive energy enlarges grain structure in the heat-affected zone, reduces toughness, and amplifies distortion. It works the other way too: too little heat gives you cold lap and lack of fusion. The fix is never “more amps” alone. Often it is a slower travel speed, correct voltage, or a different pass sequence. Material behavior matters as well, since aluminum pulls heat away from the arc far faster than steel, which is why travel-speed discipline is stressed throughout Aluminum MIG Welding: The Complete Practical Guide.

Duty Cycle: The 10-Minute Rule

Duty cycle is measured over a 10-minute period at a stated ambient temperature. A machine rated 200 amps at 60% duty can weld continuously for 6 minutes, then must rest for 4 minutes before starting again. Push past that and the machine overheats, the thermal protector trips, and repeated abuse shortens the life of the rectifiers and transformer. Long, thin extension cords make it worse by feeding the machine less voltage than it expects, so the output you actually get is lower than the dial suggests.

Interpass Temperature, Preheat and Postheat

Every qualified procedure also sets thermal limits around the weld itself. Interpass temperature is the maximum heat allowed in the base metal before the next pass is laid; exceeding it keeps the heat-affected zone at elevated temperature too long and invites grain growth and, in some alloys, cracking. Preheat slows cooling and drives off moisture, which is critical for low-hydrogen rods like 7018, while postheat or controlled cooling relieves residual stress. Alloyed and stainless work is even less forgiving of sloppy thermal control, as the filler and procedure choices in Alloy 20 Welding: Procedures, Filler Metals, and Best Practices illustrate.

Eye Protection Scales With Amperage

Amperage is a safety variable, not just a quality one. Higher current means a more intense arc and stronger ultraviolet and infrared radiation, which is why filter lenses get darker as the amps climb. OSHA’s eye-protection requirements in 1926.102 list the following progression for arc welding:

Welding current	Minimum filter shade
Under 60 amps	Shade 7
Mid-range current	Shades 8 through 10
Above 250 amps	Shade 11

Auto-darkening helmets do this electronically, but they must still be set to a shade appropriate for the current you are running. Beyond the lens, the arc’s UV output burns skin and eyes even at a distance, and welding fume needs capture at the source through ventilation or extraction. Electrical safety sits alongside it: OSHA 1910.254 covers arc welding and cutting equipment, including conductor rating and safe installation of the machines themselves.

Putting It All Together

Treat the amp chart as your entry point and the rest of the system as the check. Set the recommended current, confirm your machine has the duty-cycle headroom, control heat with travel speed rather than the dial, keep interpass limits in mind on multi-pass work, and step your lens shade up as the current rises. When a written procedure exists, it overrides every generic table you will ever find.

You have read the theory, walked through three process charts, and diagnosed the classic too-hot and too-cold failures. Now let’s compress all of it onto one card you can tape inside your machine door. Think of everything below as starting numbers, not finished answers: the chart gets you close, and your puddle gets you the rest of the way.

The One-Page Quick-Reference Card

These figures cover mild steel in the flat position on a normally fit-up joint. Use them as first dials and adjust from there.

Thickness	Stick (E7018)	MIG (0.030–0.035 in solid wire)	TIG (steel butt joint)
16 gauge (0.060 in)	35–55 A with 1/16–3/32 rod	40–70 A	30–60 A
1/8 in	90–130 A with 3/32–1/8 rod	180–210 A	110–130 A
3/16 in	110–150 A with 1/8 rod	200–250 A	140–180 A
1/4 in	130–180 A with 5/32–3/16 rod	250–300 A	190–240 A

Adjust in Small Steps and Wait for the Truth

Change one thing at a time, in 5–10 amp increments, and lay a full test bead before you judge the result. This matters more than it sounds: the puddle lags the dial by a few seconds, and the first inch of a bead often lies to you. If you crank twice while running, you will end up chasing a setting that never existed. Dial, run a complete bead on scrap, look at it, then decide.

The same patience applies to wire feed on MIG. Wire feed speed is amperage in disguise, so a jump of 25 ipm is roughly the same order of change as a 10 amp stick adjustment. When no chart is handy, the Miller rule of roughly one amp per 0.001 inch of thickness still gives you a defensible first guess.

Keep a Logbook: Your Best Chart Is Handwritten

Buy a cheap notebook and keep it next to the machine. For every job that turned out well, record:

• Material type and measured thickness
• Joint type, joint preparation, and welding position
• Electrode or wire brand, classification, and diameter
• Amperage (and voltage or wire feed speed where applicable)
• Travel speed, roughly, plus travel direction
• Polarity, gas, and the honest result: penetration, bead shape, spatter

Do this for a few months and you stop reading a generic chart and start reading your own. Machines vary, operators vary, and a setting that produces a perfect bead on your table may not on someone else’s. Logging electrode performance is especially useful when you test several alloy steel welding electrodes on the same plate and want a fair comparison.

Build a Shop-Specific Chart

1. Collect the manuals: your machine’s output chart, the electrode manufacturer’s published ranges, and your wire supplier’s parameter tables.
2. Pick the thicknesses your shop actually runs — for most small shops that is 16 gauge, 1/8, 3/16, and 1/4 inch.
3. Cut sample coupons, set up each thickness at the low end of the published range, and work upward until the bead profiles and a simple root check look right.
4. Write the winning number for your machine, your wire, and your hands onto a card and mount it on the welder.
5. Revisit the card whenever you change gas, cable length, polarity, or machine. Each of those shifts the answer.

If you run a dual-voltage or multi-process machine, build separate columns for 120 V and 240 V. Output is genuinely different at each input voltage, especially on MIG, and a single number carried across both will quietly under- or over-weld. The same caution applies when you switch processes: stick, MIG, and TIG amps are not interchangeable, and settings proven on steel will be wrong for aluminum, where prep and shielding matter as much as the dial — resources like an aluminum cleaning prep guide and an aluminum MIG setup walkthrough pay for themselves the first time you try it.

Treat the welding amp chart as a starting point, never a commandment. Set it, lay a bead, and adjust by 5–10 amps based on what the puddle tells you: wide and fluid means back off, tall and icy means add heat. Keep the logbook honest, and within a few months you will reach for your own handwritten card before any chart on the internet — which is exactly the point.

Frequently Asked Questions

What is a welding amp chart?

A welding amp chart is a reference table that matches base metal type, material thickness, welding process and electrode or wire diameter to a recommended starting amperage range. It is designed to get you into a workable zone quickly, after which you fine-tune based on puddle behavior.

How many amps per thickness of metal should I use?

For carbon steel, a common starting rule is 1 amp per 0.001 inch of thickness, so 1/8-inch (0.125) steel starts around 125 amps. Aluminum TIG often needs 20–25% more, and out-of-position work usually needs 10–15% less.

What amps should a 7018 rod run at?

A 1/8-inch E7018 is typically run in roughly the 100–150 amp range, while 5/32-inch commonly falls around 130–190 amps. Always start at the lower end of the manufacturer’s published range and increase in 5–10 amp steps.

Is amperage or voltage the main setting to change?

Amperage controls heat, penetration and deposition rate, so it is the primary variable matched to thickness. Voltage (in MIG) shapes arc length and bead profile; in stick and TIG, arc length plays the equivalent role.

Why does my amp chart give different numbers than my machine’s chart?

Generic charts assume clean steel, flat position and normal heat sinking, while manufacturer charts account for that specific power source’s output characteristics. Use the machine’s own chart first and treat generic ranges as a cross-check.

How much lower should I set amps for vertical or overhead welding?

Vertical-up and overhead joints generally need about 10–15% less current than the same joint in flat position to keep the puddle from sagging. If the bead is climbing or dripping, reduce amps before changing travel speed.

Does polarity change what amp setting I should use?

Yes. DCEP concentrates heat at the rod for deeper penetration, DCEN pushes heat into the plate and melts the filler faster, and AC splits the difference. The same rod on a different polarity can need a modest adjustment, sometimes 5–15 amps.

Can I weld without an amp chart?

You can, but you will burn a lot of scrap learning the ranges. Using the chart plus the 1 amp per 0.001-inch rule and then adjusting by observation gets you to a sound weld far faster than dialing blindly.

Do amp settings affect weld safety and code compliance?

Indirectly, yes. Amperage drives heat input, which AWS D1.1 and similar codes may limit to protect toughness and control distortion. Higher current also requires a darker filter lens — OSHA’s table ranges from shade 7 below 60 amps to shade 11 above 250 amps.