Sheet Metal Gauge Thickness Chart: Steel, Aluminum & Stainless (Inches + mm)

The sheet metal gauge system is one of the most useful — and most confusing — conventions in fabrication. It uses a single number to describe thickness, but that number behaves backwards (higher gauge = thinner metal) and means a different actual thickness depending on the material. Get it wrong and you order the wrong thickness, your parts don’t fit, and you lose weeks sorting it out.

This guide gives you the complete gauge thickness chart for steel, aluminum, and stainless steel — in both inches and millimeters — and explains how to read it and specify thickness correctly.

How the Gauge System Works

Sheet metal gauge is a standardized numbering system for thickness, but unlike millimeters or inches — which state thickness directly — gauge uses an arbitrary number that maps to a decimal thickness through standardized tables.

Two things make it tricky:

1. It’s inverse. The smaller the gauge number, the thicker the metal. 18-gauge is thicker than 20-gauge; 10-gauge is much thicker than both.
2. It’s material-specific. Different metals use different gauge standards:
   • Mild steel uses the Manufacturers’ Standard Gauge (MSG)
   • Stainless steel uses a fractional-inch-based sheet gauge
   • Aluminum uses the Brown & Sharpe (B&S) system

Because of those different standards, the same gauge number is a different thickness in each material.

The Gauge Thickness Chart

Here’s the reference chart. Values are nominal thickness in inches and millimeters. Common fabrication gauges are noted.

Steel (mild / carbon steel)

Gauge	Inches	mm
7	0.1793”	4.55
8	0.1644”	4.18
10	0.1345”	3.42
11	0.1196”	3.04
12	0.1046”	2.66
14	0.0747”	1.90
16	0.0598”	1.52
18	0.0478”	1.21
20	0.0359”	0.91
22	0.0299”	0.76
24	0.0239”	0.61

Stainless Steel

Gauge	Inches	mm
7	0.1875”	4.76
8	0.1719”	4.37
10	0.1406”	3.57
11	0.1250”	3.18
12	0.1094”	2.78
14	0.0781”	1.98
16	0.0625”	1.59
18	0.0500”	1.27
20	0.0375”	0.95
22	0.0312”	0.79
24	0.0250”	0.64

Aluminum

Gauge	Inches	mm
7	0.1443”	3.67
8	0.1285”	3.26
10	0.1019”	2.59
11	0.0907”	2.30
12	0.0808”	2.05
14	0.0641”	1.63
16	0.0508”	1.29
18	0.0403”	1.02
20	0.0320”	0.81
22	0.0253”	0.64
24	0.0201”	0.51

Galvanized steel roughly follows mild steel with a small addition for the zinc coating. Values are nominal — mill tolerances apply (see below).

Notice How Different the Same Gauge Is

Look at 16 gauge across the three materials:

16 gauge	Thickness
Stainless	1.59 mm (0.0625”)
Steel	1.52 mm (0.0598”)
Aluminum	1.29 mm (0.0508”)

That’s a meaningful spread — over 0.3 mm between stainless and aluminum at the same gauge number. This is exactly why you can’t just say “16 gauge” and assume everyone means the same thickness.

Which Gauge for What? (Common Fabrication Gauges)

• 16 and 18 gauge cover the majority of custom laser-cut work — they balance rigidity, formability, and wide material availability across steel, stainless, and aluminum.
• 14 gauge is the go-to when parts need more structural strength — brackets, frames, and mounting plates that would flex too much at 16 gauge.
• 10–12 gauge for heavy structural components (may require a different cutting process depending on material).
• 20–24 gauge for lightweight panels, covers, and parts where weight or cost matters more than rigidity.

A useful cost lever is checking whether a lighter decimal thickness can meet the released strength, stiffness, dent resistance and fastening requirements. Any saving depends on the current material quote, nesting and fabrication route. See our 9 ways to reduce cost guide.

The Costly Mistake: Specifying Gauge Without a Standard

Here’s a real-world trap. A buyer orders “16-gauge 304 stainless” from a new overseas supplier. The mill certificate shows 1.45 mm; the buyer expected 1.59 mm. Result: weeks of production delay negotiating a replacement.

The cause? The buyer specified gauge but never named the standard. The drawing referenced ASTM A480; the mill produced to GB/T 3280 tolerances. Same gauge number, different actual thickness and tolerance.

How to avoid it:

• Always specify material + standard + decimal thickness (e.g. “1.5 mm 304 stainless, ASTM A480”), not just “16 gauge.”
• Remember thickness tolerances apply — ASTM A480 permits about ±0.13 mm on 16-gauge 304 stainless, so verify delivered material with calipers.
• For quoting, CAD, and tolerance checks, decimal thickness in mm is the safest value — it’s unambiguous across suppliers and countries.

This is especially important in international sourcing, where ASTM, JIS, EN, and GB/T standards can assign slightly different thicknesses to the same gauge.

How DRAmetal Helps

We work in gauge and decimal thickness fluently, and we’ll make sure your spec is unambiguous:

• Material and thickness guidance — we’ll confirm the exact mm thickness for your part, not just a gauge number
• Standards clarity — we quote and produce to a stated standard and decimal thickness, so there’s no ambiguity
• Cost feedback — including whether a lighter gauge would save material while meeting your strength needs
• Verified material — mill certs and dimensional checks on delivered stock

As a China-based manufacturer serving global buyers, we align on the standard and decimal thickness before release. Compare our material options, laser cutting process, CNC bending process and custom sheet metal panels. For related material decisions, see our 304 vs 316 stainless and aluminum grades guides.

Need help choosing the right thickness for your part? Send us your drawing with the material standard, load case and quantity for a manufacturability and quotation review.