MIG Welding Settings Calculator & Chart (Amps, Wire, Speed)

The settings chart inside your welder's door is the best starting point for that machine. When you've lost it, bought a used welder, or want to know why the numbers are what they are, the math below gets you within tuning range. Pick a thickness and the calculator gives you amperage, the wire sizes that fit, and wire feed speed for each.

The Calculator

Starting points from Miller's published rules, not a substitute for your machine's door chart. Run a test bead on scrap of the same thickness and adjust.

Where the Numbers Come From

All three rules come from Miller Electric's guide to setting MIG parameters:

• Amperage: "Each .001 inch of material thickness requires 1 amp of output."
• Wire diameter ranges: .023 in. runs 30-130 amps, .030 in. 40-145, .035 in. 50-180, and .045 in. 75-250.
• Wire feed speed: multiply amperage by 3.5 in. per amp for .023 wire, 2 for .030, 1.6 for .035, and 1 for .045.

Gauge thicknesses use the standard manufacturers' sheet steel gauge (24 ga = 0.0239 in., 16 ga = 0.0598 in., 12 ga = 0.1046 in.).

MIG Settings Chart: Mild Steel, Solid Wire

At 3/16 in. and up, the rule outruns both common hobby wires and most 120V machines. That's where .045 wire, 240V welders, and multi-pass welds come in.

Dialing In Voltage and Travel Speed

Miller's guidance on reading the arc: if it stubs into the workpiece, increase voltage; if it's erratic and burns back at the tip, reduce it. On travel speed, going too fast leaves a narrow bead with poor tie-in, and going too slow adds excess heat, a too-wide bead, and possible burn-through on thin material. Porosity and pinholes in the weld point to missing or inadequate shielding gas.

Picking a Welder for the Job

For sheet metal through 1/8 in. steel, a 120V machine covers the amperage. The Hobart Handler 140EZ is rated 30-140A and lists 24 gauge up to 3/16 in. steel, per its listing. If you want to skip gas bottles entirely, the Lincoln Weld-Pak 90i FC is a flux-core-only machine that plugs into 120V. For heavier steel, a dual-voltage machine like the YESWELDER 140A runs on 110V or 220V, per its listing.

Common Questions

Does the 1-amp-per-thousandth rule work for flux-core?

The amperage rule is a starting point for MIG on steel generally, but flux-core wire runs on its own feed-speed numbers. Use the chart on the spool or in your welder's door for speed.

.030 or .035 wire?

Both cover the 50-145 amp middle where most home-shop work happens. By Miller's ranges, .030 reaches lower (40A) for thin sheet and .035 reaches higher (180A) for thicker steel.

Why does my machine's door chart disagree?

The door chart is tuned to that welder's transformer or inverter and its specific gun. Trust it first and use these rules to fill gaps or understand the logic.

Bottom Line

One amp per thousandth of an inch, a wire whose range covers that amperage, and wire speed by the multiplier: that's a MIG setup from first principles. Then tune voltage on scrap until the bead lays flat and ties in.