18 gauge steel thickness
18 gauge steel is 0.0478 in (1.21 mm) thick, per the Manufacturers' Standard Gauge. The same gauge number means a different thickness in other metals: galvanized steel 0.0516 in, stainless steel 0.0500 in, aluminium 0.0403 in.
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| Material | Gauge standard | Thickness (in) | Thickness (mm) | kg/m² |
|---|---|---|---|---|
| Steel (this page) | Manufacturers' Standard Gauge | 0.0478 | 1.21 | 9.53 |
| Galvanized steel | galvanized sheet gauge | 0.0516 | 1.31 | 10.29 |
| Stainless steel | U.S. Standard Gauge (stainless sheet chart) | 0.0500 | 1.27 | 10.07 |
| Aluminium | Brown & Sharpe (AWG) gauge | 0.0403 | 1.02 | 2.74 |
| Gauge | Thickness (in) | Thickness (mm) | kg/m² | lb/ft² |
|---|---|---|---|---|
| 12 ga | 0.1046 | 2.66 | 20.86 | 4.27 |
| 14 ga | 0.0747 | 1.90 | 14.89 | 3.05 |
| 16 ga | 0.0598 | 1.52 | 11.92 | 2.44 |
| 18 ga (this page) | 0.0478 | 1.21 | 9.53 | 1.95 |
| 20 ga | 0.0359 | 0.91 | 7.16 | 1.47 |
| 22 ga | 0.0299 | 0.76 | 5.96 | 1.22 |
| 24 ga | 0.0239 | 0.61 | 4.77 | 0.98 |
Practical notes
Gauge is a convention, not a unit: a higher gauge number is thinner, and steps are not even. 18 gauge is 0.0478 in for uncoated carbon steel (cold-rolled / hot-rolled sheet), but galvanized steel 0.0516 in, stainless steel 0.0500 in and aluminium 0.0403 in. Put the decimal thickness on drawings and purchase orders to avoid mix-ups.
Mills supply sheet to a thickness tolerance (ASTM A568 / A480 / EN 10131), so a measured sheet can be a few thousandths of an inch off the nominal value. Measure with a micrometer before calculating bend allowances or press-fit clearances.
Weight per area here is thickness × density (carbon steel, 7.85 g/cm³): 1.21 mm × 7.85 = 9.53 kg/m². Multiply by the sheet area for blank weight; a 4 × 8 ft sheet is 2.973 m², so about 28.3 kg (62.5 lb).
Manufacturers' Standard Gauge is based on a steel weight of 41.82 lb/ft² per inch of thickness, which is why its decimal values look irregular.
FAQ
How thick is 18 gauge steel?
0.0478 in, which is 1.21 mm, per the Manufacturers' Standard Gauge.
How thick is 18 gauge in mm?
For steel, 18 gauge is 1.21 mm. In other metals: galvanized steel 1.31 mm, stainless steel 1.27 mm, aluminium 1.02 mm.
How much does 18 gauge steel weigh?
About 9.53 kg per square metre (1.95 lb per square foot), using carbon steel, 7.85 g/cm³.
Is 18 gauge thicker than 16 gauge?
No. Higher gauge numbers are thinner: 16 ga steel is 0.0598 in, 18 ga is 0.0478 in.
Sources: Steel: Manufacturers' Standard Gauge · Densities: EN 10025 / ASTM A1008 (steel), ASTM A240 (stainless), Aluminum Association (5052) · 1 in = 25.4 mm (exact)
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