---
type: "sheet-metal-gauge"
gauge_number: "12"
material: "steel"
material_name: "Sheet Steel"
gauge_system: "MSG"
thickness_in: 0.1046
thickness_mm: 2.6572
weight_lb_per_sqft: 4.375
weight_kg_per_sqm: 21.36
standard: "15 U.S.C. 206; Manufacturers' Standard Gauge; Brown & Sharpe / AWG"
verified: "August 1, 2026"
url: https://shopmath.org/gauges/steel/12
---

# 12 Gauge Sheet Steel — Sheet Metal Thickness in Inches and Millimetres

12 gauge steel is 0.1046 in (2.657 mm) thick. That figure is on the MSG — gauge is a material-specific numbering scheme, not a unit, so the same number is a different thickness in another material.

- **Gauge**: 12
- **Material**: Sheet Steel
- **Gauge system**: MSG
- **Thickness**: 0.1046 in (2.657 mm)
- **Weight**: 4.375 lb/ft² (21.36 kg/m²)

## 12 Gauge Sheet Steel Thickness

| Property | Value |
| --- | --- |
| Thickness (in) | 0.1046 |
| Thickness (mm) | 2.657 |
| Weight (lb/ft²) | 4.375 |
| Weight (kg/m²) | 21.36 |
| Gauge system | MSG |

## 12 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](https://shopmath.org/gauges/aluminum/12.md) | B&S | 0.0808 | 2.053 |  |  |
| [Galvanized Steel](https://shopmath.org/gauges/galvanized/12.md) | galvanized-MSG | 0.1084 | 2.752 | 4.375 | 21.36 |
| Sheet Steel (this page) | MSG | 0.1046 | 2.657 | 4.375 | 21.36 |
| [U.S. Standard Gauge](https://shopmath.org/gauges/us-standard/12.md) | USG | 0.1094 | 2.778 | 4.375 | 21.36 |

## Sources and Method for 12 Gauge Sheet Steel

### Sheet Steel 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

### 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 12 Gauge Sheet Steel

### How thick is 12 gauge steel?

12 gauge steel is 0.1046 in (2.657 mm) thick, on the MSG.

### What is 12 gauge in mm?

12 gauge steel is 2.657 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 12 gauge the same thickness in every material?

No. 12 gauge is 0.1046 in in sheet steel, but 0.0808 in in sheet aluminium, 0.1084 in in galvanized steel, 0.1094 in in u.s. standard gauge. Each material uses its own gauge system: B&S; galvanized-MSG; MSG; USG.

### How much does 12 gauge steel weigh per square foot?

4.375 lb per square foot (21.36 kg per square metre).

## Related pages

- Thicker (lower gauge number): [11 gauge sheet steel](https://shopmath.org/gauges/steel/11.md) — 0.1196 in
- Thinner (higher gauge number): [13 gauge sheet steel](https://shopmath.org/gauges/steel/13.md) — 0.0897 in
- All sheet steel gauges: [Sheet Steel gauge chart](https://shopmath.org/gauges/steel.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)

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*Source: [ShopMath](https://shopmath.org/gauges/steel/12) — data verified August 1, 2026. Reference data; verify against the governing standard before manufacture.*