Buying Guide MIG Consumables MIG Welding

MIG Wire Size Chart: .023 vs .030 vs .035 vs .045 by Metal Thickness and Amperage

Choose .023, .030, .035 or .045 MIG wire by the current you weld at and the thickness of your steel, with charts for amperage, thickness and starting wire speed, and the parts to change when you switch sizes.

Published November 4, 2026

MIG welding wire sizes .023, .030, .035 and .045 in. drawn to scale with their exact diameters in millimetres

In this guide

Quick answer: Choose MIG wire by the current you weld at, and the current follows the thickness of your steel: about 1 amp for every 0.001 in. Use .023 in. wire for thin sheet, .030 in. for sheet metal up to about 1/8 in., .035 in. for most shop work up to about 3/16 in., and .045 in. for 3/16 in. and thicker.

.023 in. (0.6 mm): 30 to 130 A. Auto body panels and thin sheet.
.030 in. (0.8 mm): 40 to 145 A. Sheet metal to about 1/8 in., and small machines.
.035 in. (0.9 mm): 50 to 180 A. The most common all-round size for shop and farm work.
.045 in. (1.2 mm): 75 to 250 A. Thick steel, multi-pass welds and production work.

MIG wire size chart by amperage and metal thickness

This chart is for solid mild steel MIG wire, ER70S-6, which Canadian packaging may also show by its CSA W48 name, ER49S-6. The thickness column uses the common rule of thumb of 1 amp for every 0.001 in. of steel, for one pass.

Wire size	Current range	Steel thickness, one pass	Best for
.023 in. (0.6 mm)	30 to 130 A	22 ga to about 1/8 in. (0.8 to 3.3 mm)	Auto body, thin sheet, low-amp machines
.030 in. (0.8 mm)	40 to 145 A	18 ga to just over 1/8 in. (1.0 to 3.7 mm)	Sheet metal, light repair, small machines
.035 in. (0.9 mm)	50 to 180 A	18 ga to about 3/16 in. (1.3 to 4.6 mm)	General fabrication, farm and shop repair
.045 in. (1.2 mm)	75 to 250 A	14 ga to 1/4 in. (1.9 to 6.4 mm), thicker in several passes	Thick plate, structural work, production

Swipe sideways to see the whole drawing.

The light bar is the thickness each wire welds in one pass. The dark part is where it is the usual choice, as in the thickness table below, and hatched parts need stitch welds or several passes. The scale is stretched at the thin end so the sheet sizes are readable.

These are starting ranges, not exact limits. The joint, the welding position, your gas and your machine all change the right setting, so run a test weld on scrap of the same thickness first.

How the 1 amp rule works

For one pass on clean steel, set about 1 amp for every 0.001 in. of thickness: 1/8 in. (0.125 in.) needs about 125 A. Then pick a wire whose range covers that current with room to spare, so you can adjust both ways.

Which wire size for your metal thickness?

Steel thickness	About this much current	Wire size
24 ga (0.6 mm)	25 A	.023 in. at its lowest setting, in short stitch welds
20 ga (0.9 mm)	35 A	.023 in.
18 ga (1.2 mm)	50 A	.023 or .030 in.
16 ga (1.5 mm)	60 A	.030 or .035 in.
14 ga (1.9 mm)	75 A	.030 or .035 in.
11 ga to 1/8 in. (3.0 to 3.2 mm)	120 to 125 A	.030 or .035 in.; .035 in. has more headroom
3/16 in. (4.8 mm)	190 A	.045 in., or .035 in. in two passes
1/4 in. (6.4 mm)	250 A	.045 in., or .035 in. in several passes
3/8 in. (9.5 mm) and thicker	Over 250 A	.045 in. in several passes on a bevelled joint

Thicker than 1/4 in.?

Bevel the joint and weld it in several passes, or use spray transfer on a bigger machine. Spray transfer needs an argon-rich gas and starts at about 195 A on .035 in. wire and 285 A on .045 in. wire.

How big is the difference?

Swipe sideways to see the whole drawing.

Cut ends drawn to the same scale, with their exact diameters. A .045 in. wire is about twice as wide as a .023 in. wire and carries almost four times as much metal per inch. Lengths are for solid steel wire.

A thicker wire feeds more metal into the joint for every inch, so it fills bigger welds faster. It also needs more current to melt, which is why each size has its own range. The same weight of wire also gets shorter as the wire gets thicker: 1 kg of .035 in. wire is about 205 m long, and 1 kg of .045 in. wire about 125 m.

Starting wire speed for each wire size

On a MIG machine, wire speed sets the current. Multiply your target current by the figure for your wire to get a starting wire speed, then fine-tune the speed and voltage on scrap.

Wire size	Wire speed per amp	Starting speed at 125 A (1/8 in. steel)
.023 in. (0.6 mm)	3.5 in./min	About 440 in./min (11.1 m/min)
.030 in. (0.8 mm)	2 in./min	250 in./min (6.4 m/min)
.035 in. (0.9 mm)	1.6 in./min	200 in./min (5.1 m/min)
.045 in. (1.2 mm)	1 in./min	125 in./min (3.2 m/min)

The settings chart on your machine, often inside the wire compartment door, gives closer starting points for your wire and gas.

.023 vs .030 vs .035 vs .045: benefits and disadvantages

Wire size	Benefits	Disadvantages
.023 in.	Lowest heat, so less burn-through and warping on thin sheet Runs on low-amp machines	Too small for thick steel Thin, soft wire kinks and tangles more easily
.030 in.	Good on sheet metal and light repair Runs well on small machines	Slow on 3/16 in. and thicker Less stiff than .035 in. wire in long gun cables
.035 in.	Widest useful range, from 18 ga to about 3/16 in. The most common size, easy to find in every spool size	Can burn through very thin sheet The top of its range is more than many small machines deliver
.045 in.	Lays down the most metal for thick steel and long welds Stiff wire that feeds well	Needs a bigger machine and a heavier gun Too hot for sheet metal

Solid wire or gasless flux-cored wire?

Both come in the common .030, .035 and .045 in. sizes. The difference is how the weld is shielded from the air.

Feature	Solid wire, with gas	Gasless flux-cored wire
How it's shielded	Shielding gas from a cylinder	Flux inside the wire, no cylinder
Benefits	Clean welds with little spatter and no slag Better on thin sheet and where looks matter	Works outdoors, where wind would blow gas away Deeper penetration, and more forgiving of light rust and mill scale
Disadvantages	Needs a gas cylinder and regulator Wind outdoors can cause porosity	Slag to chip off, more spatter and more smoke Harder to control on thin sheet
Polarity	DC electrode positive	Most run DC electrode negative; check the spool label
Drive roll	V-groove	Knurled V-groove

Shop steel MIG wire and flux-cored wire.

Aluminum and stainless steel wire

Stainless steel MIG wire comes in the same common sizes as mild steel wire. Aluminum wire is soft and buckles when it is pushed, so it feeds best through a spool gun or push-pull gun, with a U-groove drive roll and a contact tip made for aluminum.

Change these parts when you change wire size

Contact tip: the bore must match the wire, such as a .035 in. tip for .035 in. wire. See our contact tip and nozzle compatibility guide, or shop contact tips.
Drive roll: the groove must match the wire size and type: V-groove for solid steel, knurled for flux-cored, U-groove for aluminum. Many drive rolls have two grooves, so turn the roll to the right one.
Liner: it must suit the wire size. A liner that is too large lets small wire kink; one that is too small makes the wire drag. Shop liners.
Settings: reset wire speed and voltage, starting from your machine's chart or the table above.

Swipe sideways to see the whole drawing.

Top: cross-sections through the drive rolls, with red dots where the wire is gripped. Bottom: the end of a contact tip, where the bore must be just larger than the wire.

Long gun cables make small and soft wire harder to push. See What size MIG gun do I need? for cable lengths that feed well.

Safety when you change wire or drive rolls

Turn the machine off before you load wire, change drive rolls or change the contact tip.

On most machines the wire is electrically live whenever the trigger is pressed. Keep your fingers clear of the drive rolls when you feed new wire, and point the gun away from yourself and others. Cut wire with pliers and hold the loose end when you take it off the spool, because it springs. In Canada, CSA W117.2 covers safety in welding, cutting and allied processes. Always follow your machine manual.

Frequently asked questions

What size MIG wire should I use?

Match the wire to the current your work needs, about 1 amp for every 0.001 in. of steel. For most shop work from 18 ga to about 3/16 in., .035 in. wire is the safe choice. Use .023 or .030 in. for thin sheet and small machines, and .045 in. for thick steel.

Is .030 or .035 MIG wire better?

Neither is better for every job. .030 in. wire runs at lower current, so it suits sheet metal and small machines. .035 in. wire covers a wider range and lays down more metal, so it suits general fabrication up to about 3/16 in.

What size MIG wire for 1/8 inch steel?

1/8 in. steel needs about 125 A. Both .030 and .035 in. wire cover that. .035 in. gives you more headroom if you also weld thicker parts.

What size MIG wire for 1/4 inch steel?

About 250 A in one pass, which suits .045 in. wire on a machine that can deliver it. On a smaller machine, bevel the joint and weld it in several passes with .035 in. wire.

What MIG wire is best for auto body sheet metal?

.023 in. wire at a low setting. Use short tacks and stitch welds, and let the panel cool between them to avoid burn-through and warping.

How many amps do I need to MIG weld steel?

As a starting point, 1 amp for every 0.001 in. of thickness: about 60 A for 16 ga, 125 A for 1/8 in. and 250 A for 1/4 in. Adjust after a test weld on scrap.

Can I use .035 wire with a .030 contact tip?

No. Wire drags and jams in a tip that is too small, and wanders in one that is too large, which makes the arc unstable. Change the tip whenever you change wire size.

Do I need different drive rolls for different wire sizes?

Yes. The groove must match the wire size and type: V-groove for solid steel, knurled for flux-cored and U-groove for aluminum.

What size flux-cored wire should I use?

Gasless flux-cored wire usually comes in .030, .035 and .045 in. It runs at different settings from solid wire and penetrates deeper for its size, so start from the current range on the spool label.

Not sure which wire suits your machine?

Email a photo of your machine's rating plate to orders@mapindpro.com, call 905-919-1177, or visit our Toronto counter. We'll help you match the wire, contact tip and drive roll.

Email us Call 905-919-1177 Shop MIG wire

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