---
title: "Sheet Metal Gauge Chart: Steel, Galvanized, Stainless, Aluminum"
description: "mm and inch thickness for every gauge number, why aluminum is not steel, and how to stop ordering the wrong sheet."
image: "https://nestingcalc.com/og-default.png"
url: "https://nestingcalc.com/guides/sheet-metal-gauge-chart/"
locale: "en"
---

# Sheet Metal Gauge Chart: Steel, Galvanized, Stainless, Aluminum

mm and inch thickness for every gauge number, why aluminum is not steel, and how to stop ordering the wrong sheet.

## 1\. What gauge actually means

Gauge is a thickness number inherited from the old wire-drawing tradition: it counted how many passes a wire took through a draw plate. For sheet metal the rule is the opposite of what intuition suggests — a HIGHER gauge means a THINNER sheet. In the US, the Manufacturers' Standard Gauge (MSG) system is defined by weight, not by direct measurement: 41.82 lb per square foot for every inch of thickness, so steel gauge numbers trace back to a weight-based scale.

## 2\. The chart: gauge to mm by material

Thickness in millimeters by material — same gauge number, four different sheets:

| Gauge | Steel | Galvanized | Stainless | Aluminum |
| --- | --- | --- | --- | --- |
| 10 | 3.42 | 3.51 | 3.57 | 2.59 |
| 12 | 2.66 | 2.75 | 2.78 | 2.05 |
| 14 | 1.90 | 1.99 | 1.98 | 1.63 |
| 16 | 1.52 | 1.61 | 1.59 | 1.29 |
| 18 | 1.21 | 1.31 | 1.27 | 1.02 |
| 20 | 0.91 | 1.01 | 0.95 | 0.81 |
| 22 | 0.76 | 0.85 | 0.79 | 0.64 |
| 24 | 0.61 | 0.70 | 0.64 | 0.51 |

(all values in mm)

## 3\. Steel sheet gauge chart: mm, inches, kg/m²

Manufacturer's Standard Gauge for plain sheet steel; weight at 7.85 kg per m² per mm:

| Gauge | mm | inch | kg/m² |
| --- | --- | --- | --- |
| 6 | 4.94 | 0.1943 | 38.8 |
| 7 | 4.55 | 0.1793 | 35.7 |
| 8 | 4.18 | 0.1644 | 32.8 |
| 9 | 3.80 | 0.1495 | 29.8 |
| 10 | 3.42 | 0.1345 | 26.8 |
| 11 | 3.04 | 0.1196 | 23.8 |
| 12 | 2.66 | 0.1046 | 20.8 |
| 13 | 2.28 | 0.0897 | 17.9 |
| 14 | 1.90 | 0.0747 | 14.9 |
| 15 | 1.71 | 0.0673 | 13.4 |
| 16 | 1.52 | 0.0598 | 11.9 |
| 17 | 1.37 | 0.0538 | 10.7 |
| 18 | 1.21 | 0.0478 | 9.5 |
| 19 | 1.06 | 0.0418 | 8.3 |
| 20 | 0.91 | 0.0359 | 7.2 |
| 21 | 0.84 | 0.0329 | 6.6 |
| 22 | 0.76 | 0.0299 | 6.0 |
| 23 | 0.68 | 0.0269 | 5.4 |
| 24 | 0.61 | 0.0239 | 4.8 |
| 25 | 0.53 | 0.0209 | 4.2 |
| 26 | 0.46 | 0.0179 | 3.6 |
| 27 | 0.42 | 0.0164 | 3.3 |
| 28 | 0.38 | 0.0149 | 3.0 |
| 29 | 0.34 | 0.0135 | 2.7 |
| 30 | 0.30 | 0.0120 | 2.4 |
| 31 | 0.27 | 0.0105 | 2.1 |
| 32 | 0.25 | 0.0097 | 1.9 |
| 33 | 0.23 | 0.0090 | 1.8 |
| 34 | 0.21 | 0.0082 | 1.6 |

## 4\. Galvanized sheet: why the numbers shift

Galvanised sheet has its own standard because the zinc coating counts toward the gauge: 16 gauge galvanized is 1.61 mm against 1.52 mm for plain steel; 20 gauge is 1.01 mm against 0.91 mm.

| Gauge | mm | inch |
| --- | --- | --- |
| 8 | 4.27 | 0.1680 |
| 10 | 3.51 | 0.1382 |
| 12 | 2.75 | 0.1084 |
| 14 | 1.99 | 0.0785 |
| 16 | 1.61 | 0.0635 |
| 18 | 1.31 | 0.0516 |
| 20 | 1.01 | 0.0396 |
| 22 | 0.85 | 0.0336 |
| 24 | 0.70 | 0.0276 |
| 26 | 0.55 | 0.0217 |
| 28 | 0.48 | 0.0187 |

Aluminium uses yet another system (Brown & Sharpe): 16 gauge aluminium is 1.29 mm, 14 gauge 1.63 mm, 20 gauge 0.81 mm. When a drawing says 16 gauge, ask which material — the word alone is ambiguous.

## 5\. The costly mistake: gauge is not a material

Gauge alone does not define a thickness — it only means something together with the material. 16 gauge steel is 1.52 mm, but 16 gauge aluminum is only 1.29 mm, about 15% thinner. A classic HVAC story: a shop orders 16 ga sheet for ductwork, receives aluminum instead of steel, and the whole run comes out floppy and out of spec. Always specify material AND thickness in mm — "1.5 mm galvanized steel", never just "16 gauge".

## 6\. Gauge vs AWG vs SWG

Three different gauge systems are often confused. Sheet metal uses the Manufacturers' Standard Gauge; AWG (American Wire Gauge) sizes electrical wire; SWG (Imperial Standard Wire Gauge) is the old British standard. A 16 AWG wire and a 16 gauge sheet have nothing in common. ASTM A480, the standard for stainless sheet, explicitly discourages gauge numbers and calls the term archaic — order by decimal inch or mm.

## 7\. 15/10ème, chapa 16 and other local conventions

Not every country speaks gauge. France often states thickness in tenths of a millimetre: 15/10ème is 1.5 mm, 20/10ème is 2.0 mm. Brazil and Portugal use the chapa number — chapa 16 is about 1.5 mm of black steel sheet, close to 16 gauge steel but a different standard, so convert rather than assume. Germany and most of Europe state millimetres outright. Anchor points:

| Convention | Meaning | mm |
| --- | --- | --- |
| 10/10ème | One millimetre | 1.0 |
| 15/10ème · chapa 16 · 16 gauge steel | General-purpose sheet | 1.5 |
| 20/10ème | Two millimetres | 2.0 |
| 25/10ème | Light plate | 2.5 |

## 8\. A practical workflow

Measure the old sheet with a caliper in mm, order in mm, and convert back to gauge only when an older spec sheet forces you to. When in doubt, write both on the order: gauge for the shop floor, mm for the invoice. The [Sheet metal gauge](https://nestingcalc.com/sheet-metal-gauge/) converts both ways for steel, galvanized, stainless and aluminum and adds sheet weight, so quotes and orders always match.

## 9\. How thick is…? Gauge quick answers

The gauge questions asked most, answered in one place: **16 gauge** steel is 1.52 mm (0.0598 in); **14 gauge** 1.90 mm; **12 gauge** 2.66 mm; **10 gauge** 3.42 mm; **18 gauge** 1.21 mm; **20 gauge** 0.91 mm; **22 gauge** 0.76 mm; **24 gauge** 0.61 mm; **26 gauge** 0.46 mm. All values are plain sheet steel: galvanized runs 0.05–0.10 mm thicker at the same gauge, aluminium follows a different standard.

[Sheet metal gauge](https://nestingcalc.com/sheet-metal-gauge/) [Open the linear cutting calculator](https://nestingcalc.com/linear-cutting-calculator/)

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