How is wire feed speed related to amperage?

On a MIG machine the wire feed speed sets the current. Each wire diameter has a burn-off constant in in/min per amp, and feed speed equals that constant times the amperage. Smaller wire needs more feed speed for the same amps because it melts faster.

Why does deposition rate matter?

Deposition rate in pounds per hour tells you how fast you lay down weld metal, which drives labor cost and how long a job takes. It is the feed speed times the wire cross-section times steel density, adjusted for wire type.

Are solid and flux-core wires different?

Yes. Flux-core wires deposit slightly more metal per amp because of higher current density and the metal content of the core, so the tool applies a small efficiency bump for flux-core compared with solid ER70S wire.

Does this set my voltage too?

No. Feed speed and amperage control penetration and burn-off, while voltage controls arc length and bead shape. Set voltage separately to get a smooth arc and the bead profile you want for the joint.

How accurate are these numbers?

The burn-off constants match published manufacturer WFS-versus-amperage charts within a few percent for carbon steel. Treat the result as a reliable starting point and fine-tune on a test coupon for your exact machine and shielding gas.

MIG Wire Feed Speed Calculator

MIG welders run wire feed speed and amperage as effectively one control: the faster the wire feeds, the more current the arc draws to melt it. This calculator converts a target amperage into the wire feed speed your machine needs, and reports how fast you will deposit weld metal.

How it works

Each wire diameter has a published burn-off constant k in inches per minute per amp. Wire feed speed and deposition rate are then:

WFS (in/min)        = k(diameter) × amps
deposition (lb/hr)  = WFS × 60 × wire_area × 0.2836 lb/in³ × efficiency

The burn-off constant is larger for thinner wire because a smaller cross-section melts faster at a given current. Flux-core wire gets a small efficiency factor because it deposits slightly more metal per amp than solid wire.

Example and tips

Running 180 amps on .035 solid wire gives about 254 in/min of feed and roughly 6 lb/hr of deposition. If you switch to .045 wire at the same amperage the feed speed drops to about 153 in/min because the heavier wire carries more metal per inch. Always confirm settings on a scrap coupon: shielding gas mix, stickout, and joint geometry all shift the ideal voltage and travel speed that pair with these feed numbers.