---
type: "sheet-metal-gauge"
gauge_number: "31"
material: "aluminum"
material_name: "Sheet Aluminium"
gauge_system: "B&S"
thickness_in: 0.0089
thickness_mm: 0.2268
standard: "15 U.S.C. 206; Manufacturers' Standard Gauge; Brown & Sharpe / AWG"
verified: "August 1, 2026"
url: https://shopmath.org/gauges/aluminum/31
---

# 31 Gauge Sheet Aluminium — Sheet Metal Thickness in Inches and Millimetres

31 gauge aluminium is 0.0089 in (0.227 mm) thick. That figure is on the B&S — gauge is a material-specific numbering scheme, not a unit, so the same number is a different thickness in another material.

- **Gauge**: 31
- **Material**: Sheet Aluminium
- **Gauge system**: B&S
- **Thickness**: 0.0089 in (0.227 mm)

## 31 Gauge Sheet Aluminium Thickness

| Property | Value |
| --- | --- |
| Thickness (in) | 0.0089 |
| Thickness (mm) | 0.227 |
| Gauge system | B&S |

## 31 Gauge Across Materials

The same gauge number in every material this reference covers. They differ because each material carries its own gauge system, not because one chart is wrong.

| Material | Gauge system | Thickness (in) | Thickness (mm) | lb/ft² | kg/m² |
| --- | --- | --- | --- | --- | --- |
| Sheet Aluminium (this page) | B&S | 0.0089 | 0.227 |  |  |
| [Galvanized Steel](https://shopmath.org/gauges/galvanized/31.md) | galvanized-MSG | 0.0142 | 0.361 | 0.438 | 2.14 |
| [Sheet Steel](https://shopmath.org/gauges/steel/31.md) | MSG | 0.0105 | 0.266 | 0.438 | 2.14 |
| [U.S. Standard Gauge](https://shopmath.org/gauges/us-standard/31.md) | USG | 0.0109 | 0.278 | 0.438 | 2.14 |

## Sources and Method for 31 Gauge Sheet Aluminium

### Sheet Aluminium gauge thicknesses

- **Source**: 15 U.S.C. 206 (Act of Mar. 3, 1893, ch. 221, 27 Stat. 746) — U.S. Standard Gauge for sheet and plate iron and steel; 15 U.S.C. 206 statutory weights; MSG (41.82 lb/ft2 per inch), galvanized zinc allowance, and Brown & Sharpe formula per docs/research/data-sourcing.md §3.7
- **Method**: computed
- **Verified against**: Wikipedia Sheet metal, Standard sheet metal gauges table (CC BY-SA 4.0) — 137/137 checks passed at 0.05 mil

### Formulas

**Brown & Sharpe geometric series**

```text
t(n)  =  0.325 × (0.890525)^n   inches
```

_The AWG / Brown & Sharpe series used for aluminium and other non-ferrous sheet._

### Assumptions

- Gauge is a numbering scheme, not a unit. A thickness is only meaningful with its material and gauge system stated.
- Sheet is supplied to a mill tolerance around these nominal thicknesses; measure the stock when the fit matters.
- Dataset scope: EXCLUDED: stainless steel (genuinely ambiguous convention, only one source in hand), zinc, copper, brass, steel tube wall.

**Data last verified**: August 1, 2026

## Common Questions About 31 Gauge Sheet Aluminium

### How thick is 31 gauge aluminium?

31 gauge aluminium is 0.0089 in (0.227 mm) thick, on the B&S.

### What is 31 gauge in mm?

31 gauge aluminium is 0.227 mm. Gauge is not a unit — the same number means a different thickness in a different material, so the material has to be stated with it.

### Is 31 gauge the same thickness in every material?

No. 31 gauge is 0.0089 in in sheet aluminium, but 0.0142 in in galvanized steel, 0.0105 in in sheet steel, 0.0109 in in u.s. standard gauge. Each material uses its own gauge system: B&S; galvanized-MSG; MSG; USG.

## Related pages

- Thicker (lower gauge number): [30 gauge sheet aluminium](https://shopmath.org/gauges/aluminum/30.md) — 0.0100 in
- Thinner (higher gauge number): [32 gauge sheet aluminium](https://shopmath.org/gauges/aluminum/32.md) — 0.0080 in
- All sheet aluminium gauges: [Sheet Aluminium gauge chart](https://shopmath.org/gauges/aluminum.md)
- All materials and gauges: [Sheet metal gauge reference](https://shopmath.org/gauges.md)
- Full cross-material chart: [Sheet metal gauge chart](https://shopmath.org/charts/sheet-metal-gauge.md)

---

*Source: [ShopMath](https://shopmath.org/gauges/aluminum/31) — data verified August 1, 2026. Reference data; verify against the governing standard before manufacture.*