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MIG Welding Settings Calculator (Amps, Volts, Wire Speed)

Get a starting-point MIG welding voltage, amperage and wire feed speed from metal thickness, wire diameter and material — mild steel, stainless or aluminum.

Built and maintained by Paul Clark, Redmoon Software · Checked against what this tool computes on

Recommended Amperage
—
Run at — with a wire feed speed of —
SettingValue
Quick reference

These numbers are short-circuit MIG transfer starting points pulled from standard welding wire-feed-speed charts, based on your metal thickness — not a single correct answer for your exact machine, wire brand and stick-out.

Always run a test bead on scrap of the same thickness and material before welding the real piece. Listen to the arc: a steady, even crackle like frying bacon means you're close. A loud, harsh buzz with heavy spatter means you're running too hot — back off voltage or wire speed. Popping, stubbing or the wire shoving into the puddle means you're too cold, or your wire feed speed is too low for the voltage.

Aluminum runs hot and feeds fast, and the soft wire tends to tangle ("birdnest") in a standard liner — a spool gun or push-pull gun is strongly recommended for anything beyond short runs.

How it works

The output is a chart lookup, not a physical model. A seven-row short-circuit MIG transfer table for mild steel maps thickness in millimetres to amps, volts and wire feed speed — 0.8 mm at 40 A, 15.5 V and 125 ipm, rising through 3.2 mm at 140 A and 19.5 V, up to 10 mm at 225 A, 25 V and 500 ipm. Thicknesses between rows are linearly interpolated and anything outside is clamped to the end row. Inches convert at 25.4, and wire speed is also shown in m/min at 0.0254 per ipm.

Thickness does nearly all the work; the material select simply rescales the result. Mild Steel is the unmodified chart, Stainless Steel drops amperage to 0.9 times, and Aluminum raises amps to 1.15, volts to 1.05 and wire feed speed to 1.2 times. The recommended wire diameter is taken from the matched thickness row and snapped to the nearest size that material supports, and Aluminum offers only 0.9 mm and 1.2 mm. Shielding gas is fixed per material, from 75/25 argon/CO₂ for mild steel to 100 percent argon for aluminum.

These are short-circuit transfer starting points only. Spray transfer, pulsed MIG and gasless flux-core all need different settings and none are covered. Joint type, welding position, stick-out length, gas flow rate, wire brand and your machine's own calibration are not modelled, and the aluminum figures are flat multipliers on a steel chart rather than an aluminum-specific one. Run a test bead on scrap of the same thickness and material first: a steady crackle means you are close, heavy spatter means too hot, stubbing means too cold.

Frequently asked questions

What amperage should I run on 1/8 inch mild steel?

Switch Unit to inches and enter 0.125, or enter 3.175 in millimetres. Interpolating between the 2.5 mm and 3.2 mm chart rows gives roughly 139 A at 19.5 V with a wire feed speed near 323 ipm, which is about 8.2 metres per minute.

Which shielding gas should I use for stainless steel?

The tool recommends a tri-mix of 90 percent helium, 7.5 percent argon and 2.5 percent CO₂, or 98/2 argon/CO₂ as the simpler alternative. It also drops amperage to 0.9 times the mild steel figure, because stainless conducts heat away more slowly and distorts easily.

Do MIG settings really change that much for aluminium?

Yes. Aluminum runs 15 percent hotter on amps, 5 percent higher on volts and 20 percent faster on wire feed than mild steel of the same thickness, on 100 percent argon. The soft wire also birdnests in a standard liner, so a spool gun or push-pull gun is strongly advised.

Why do the numbers stop changing above 10 mm thickness?

Because 10 mm is the last row of the chart and anything thicker is clamped to it, at 225 A and 25 V. Past roughly that thickness short-circuit MIG is the wrong process anyway; you want spray transfer, multi-pass with a bevel prep, or a different machine class.

How do I convert wire feed speed from ipm to metres per minute?

Multiply inches per minute by 0.0254. The results table already prints both, so 300 ipm shows as 7.62 m/min. Older North American machines are marked in ipm while most European and modern inverter machines are dialled in m/min.

Wire size, thickness and amperage move together

MIG settings are three interlocking variables: wire diameter, material thickness and current. The widely used starting point is roughly one amp per thousandth of an inch of steel thickness, and wire size sets the usable current band — 0.6 mm wire runs comfortably at low currents for thin sheet, 0.8 mm covers a broader middle range, and thicker wire needs more current than thin material can absorb without burning through.

That is why wire choice is a decision about the work rather than about what is on the machine.

Settings are a starting point; the test piece is the answer

Every real weld departs from a chart. Joint type changes heat input — a fillet in a corner traps heat that a butt joint on a flat plate sheds — and position matters, since overhead and vertical work need lower settings to control the puddle. Shielding gas composition changes the arc characteristics and therefore the voltage that runs smoothly.

Machines also differ. Two welders set to nominally identical numbers do not necessarily deliver the same arc, particularly across manufacturers and between transformer and inverter machines.

Use these figures to get close on a scrap piece of the same material and thickness, then tune by sound and bead appearance. A settings calculator saves you the first three test welds; it does not replace them.

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