Sheet Metal Gauge Thickness Chart & Converter

Convert sheet metal gauge to thickness in both millimetres and inches, for standard steel, galvanized steel, stainless steel and aluminum. Gauge is inverse to thickness — a higher gauge number means a thinner sheet — and each material uses its own gauge standard, so always convert against the correct table.

Gauge → Thickness

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Thickness → Nearest Gauge

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Nominal values from published gauge standards. Mill tolerances apply — check the mill certificate for exact thickness.

Sheet metal gauge chart (all materials)

Gauge Steel (in / mm) Galvanized (in / mm) Stainless (in / mm) Aluminum (in / mm)
3 0.2391 / 6.07 — 0.2500 / 6.35 0.2294 / 5.83
4 0.2242 / 5.69 — 0.2344 / 5.95 0.2043 / 5.19
5 0.2092 / 5.31 — 0.2187 / 5.55 0.1819 / 4.62
6 0.1943 / 4.94 — 0.2031 / 5.16 0.1620 / 4.11
7 0.1793 / 4.55 — 0.1875 / 4.76 0.1443 / 3.67
8 0.1644 / 4.18 0.1681 / 4.27 0.1719 / 4.37 0.1285 / 3.26
9 0.1495 / 3.80 0.1532 / 3.89 0.1563 / 3.97 0.1144 / 2.91
10 0.1345 / 3.42 0.1382 / 3.51 0.1406 / 3.57 0.1019 / 2.59
11 0.1196 / 3.04 0.1233 / 3.13 0.1250 / 3.17 0.0907 / 2.30
12 0.1046 / 2.66 0.1084 / 2.75 0.1094 / 2.78 0.0808 / 2.05
13 0.0897 / 2.28 0.0934 / 2.37 0.0938 / 2.38 0.0720 / 1.83
14 0.0747 / 1.90 0.0785 / 1.99 0.0781 / 1.98 0.0641 / 1.63
15 0.0673 / 1.71 0.0710 / 1.80 0.0703 / 1.79 0.0571 / 1.45
16 0.0598 / 1.52 0.0635 / 1.61 0.0625 / 1.59 0.0508 / 1.29
17 0.0538 / 1.37 0.0575 / 1.46 0.0563 / 1.43 0.0453 / 1.15
18 0.0478 / 1.21 0.0516 / 1.31 0.0500 / 1.27 0.0403 / 1.02
19 0.0418 / 1.06 0.0456 / 1.16 0.0438 / 1.11 0.0359 / 0.91
20 0.0359 / 0.91 0.0396 / 1.01 0.0375 / 0.95 0.0320 / 0.81
21 0.0329 / 0.84 0.0366 / 0.93 0.0344 / 0.87 0.0285 / 0.72
22 0.0299 / 0.76 0.0336 / 0.85 0.0313 / 0.80 0.0253 / 0.64
23 0.0269 / 0.68 0.0306 / 0.78 0.0281 / 0.71 0.0226 / 0.57
24 0.0239 / 0.61 0.0276 / 0.70 0.0250 / 0.64 0.0201 / 0.51
25 0.0209 / 0.53 0.0247 / 0.63 0.0219 / 0.56 0.0179 / 0.45
26 0.0179 / 0.45 0.0217 / 0.55 0.0188 / 0.48 0.0159 / 0.40
27 0.0164 / 0.42 0.0202 / 0.51 0.0172 / 0.44 0.0142 / 0.36
28 0.0149 / 0.38 0.0187 / 0.47 0.0156 / 0.40 0.0126 / 0.32
29 0.0135 / 0.34 0.0172 / 0.44 0.0141 / 0.36 0.0113 / 0.29
30 0.0120 / 0.30 0.0157 / 0.40 0.0125 / 0.32 0.0100 / 0.25

How gauge works

Sheet metal gauge originated from the number of drawing operations used to reduce a sheet, which is why the scale is inverse and why it is not a single decimal system. Standard steel follows the Manufacturers' Standard Gauge, aluminum follows the Brown & Sharpe (B&S) system, and galvanized sheet is heavier at the same gauge because the zinc coating adds thickness. Stainless has its own table again. For this reason a "14 gauge" part is not one thickness — it is 1.90 mm in steel but 1.63 mm in aluminum.

Frequently asked questions

How thick is 14 gauge steel?

14 gauge standard steel is 0.0747 in (1.90 mm). In stainless it is 0.0781 in (1.98 mm), galvanized 0.0785 in (1.99 mm), and aluminum 0.0641 in (1.63 mm).

Is a higher gauge number thicker or thinner?

Thinner. Sheet metal gauge runs inverse to thickness: the higher the gauge number, the thinner the sheet. 10 gauge is much thicker than 20 gauge.

Why does the same gauge differ between steel and aluminum?

Gauge is not a single universal standard. Steel uses the Manufacturers' Standard Gauge, aluminum uses the Brown & Sharpe (B&S) system, and galvanized sheet adds zinc coating thickness, so each material has its own table.

How do I convert gauge to mm?

Look up the gauge in the table for your material to get thickness in inches, then multiply by 25.4 to get millimetres. This converter does it automatically.

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