21 gauge steel thickness and weight
0.0329 in · 0.84 mm · 1.344 lb/ft²
21 gauge sheet steel (Manufacturers' Standard Gauge) is 0.0329 in, or 0.84 mm, thick. It weighs 1.344 lb per square foot (6.56 kg/m²).
Weight of common sheet sizes
| Sheet | lb | kg |
|---|---|---|
| 4 × 8 ft | 43.0 | 19.5 |
| 4 × 10 ft | 53.7 | 24.4 |
| 5 × 10 ft | 67.2 | 30.5 |
| 1000 × 2000 mm | 28.9 | 13.1 |
| 1250 × 2500 mm | 45.2 | 20.5 |
| 1500 × 3000 mm | 65.1 | 29.5 |
21 gauge in other metals
| Material | Thickness (in) | Thickness (mm) | kg/m² |
|---|---|---|---|
| Sheet steel | 0.0329 | 0.84 | 6.56 |
| Galvanized steel | 0.0366 | 0.93 | 7.30 |
| Stainless steel | 0.034 | 0.86 | 6.85 |
| Aluminum | 0.028 | 0.71 | 1.92 |
Gauge numbers are tied to the material, so 21 gauge aluminum is not the same thickness as 21 gauge steel. When ordering, give the thickness in inches or millimetres.
Compared with nearby gauges
| Gauge | in | mm | lb/ft² | Thickness vs 21 ga |
|---|---|---|---|---|
| 18 gauge | 0.0478 | 1.21 | 1.952 | +45 % |
| 19 gauge | 0.0418 | 1.06 | 1.707 | +27 % |
| 20 gauge | 0.0359 | 0.91 | 1.466 | +9 % |
| 21 gauge | 0.0329 | 0.84 | 1.344 | — |
| 22 gauge | 0.0299 | 0.76 | 1.221 | −9 % |
| 23 gauge | 0.0269 | 0.68 | 1.099 | −18 % |
| 24 gauge | 0.0239 | 0.61 | 0.976 | −27 % |
A lower gauge number means a thicker sheet. The steps between gauges are not equal, because the gauge system started as a measure of weight per square foot rather than of thickness.
Metric and fractional equivalents
Outside the US, sheet is ordered in millimetres. The nearest standard metric thickness to 21 gauge (0.84 mm) is 0.8 mm, which weighs 6.28 kg/m². If a drawing calls for 21 gauge and you buy metric sheet, check whether the small difference in thickness matters for bending, welding or fit.
Weight of strips
Weight per running foot of a 21 gauge strip, for sheared blanks and formed parts.
| Strip width | lb per foot of length |
|---|---|
| 6 in | 0.67 |
| 12 in | 1.34 |
| 24 in | 2.69 |
| 36 in | 4.03 |
| 48 in | 5.37 |
Where 21 gauge is used
This range is common for appliance housings, electrical boxes, ducting, flashing and automotive panels. Thickness tolerances for cold-rolled and hot-rolled sheet are set by ASTM A568 and depend on width, so the measured thickness can be a few thousandths of an inch off the nominal gauge value.
Frequently asked questions
How thick is 21 gauge steel in mm?
21 gauge sheet steel is 0.84 mm (0.0329 in). The nearest standard metric sheet is 0.8 mm.
How much does a 4 × 8 sheet of 21 gauge steel weigh?
About 43.0 lb (19.5 kg): 1.344 lb/ft² × 32 ft².
Is 21 gauge thicker than 22 gauge?
Yes. A lower gauge number is thicker: 21 gauge is 0.0329 in, 22 gauge is 0.0299 in, and 20 gauge is 0.0359 in.
How thick is 21 gauge galvanized steel?
0.0366 in (0.93 mm), slightly more than plain 21 gauge because the gauge includes the zinc coating.
Is 21 gauge aluminum the same thickness as steel?
No. 21 gauge aluminum is 0.028 in (0.71 mm); aluminum uses a different gauge table.
Full sheet metal gauge chart · Steel plate weight chart · Steel weight calculator
Data adapted from Wikipedia, "Sheet metal" (CC BY-SA 4.0).