Steel Sheet Thickness and Gauge Chart (Gauge to mm)
Steel sheet gauge to millimetre chart for standard and galvanized sheet, why gauge numbers mislead, and why buyers in Saudi Arabia should specify thickness in mm.
Saudi Steel Work Editorial Team · · 3 min read
Short answer: Gauge is a traditional numbering system where higher numbers mean thinner sheet; for example 16 gauge standard steel is about 1.52 mm and 20 gauge about 0.91 mm. Because different gauge systems exist for standard, galvanized and stainless sheet, buyers should always specify thickness in millimetres.
Gauge numbers still appear in specifications and conversations, especially for ducting, roofing and fabrication. But gauge is ambiguous — and in a metric market like Saudi Arabia, millimetres are the safer choice.
Standard steel sheet gauge (approximate)
| Gauge | Thickness (in) | Thickness (mm) | Weight (kg/m²) |
|---|---|---|---|
| 10 | 0.1345 | 3.42 | 26.8 |
| 11 | 0.1196 | 3.04 | 23.9 |
| 12 | 0.1046 | 2.66 | 20.9 |
| 14 | 0.0747 | 1.90 | 14.9 |
| 16 | 0.0598 | 1.52 | 11.9 |
| 18 | 0.0478 | 1.21 | 9.5 |
| 20 | 0.0359 | 0.91 | 7.2 |
| 22 | 0.0299 | 0.76 | 6.0 |
| 24 | 0.0239 | 0.61 | 4.8 |
| 26 | 0.0179 | 0.45 | 3.6 |
Weights are calculated at 7.85 kg/m² per mm for uncoated steel.
Why gauge causes problems
- Higher gauge = thinner — counter-intuitive for new buyers
- Different systems exist for standard steel, galvanized steel, stainless steel and aluminium
- Steps between gauges are uneven
- Suppliers may round to the nearest metric thickness differently
Specify in millimetres
Write "1.5 mm GI sheet Z275, DX51D" rather than "16 gauge GI". Include the tolerance standard if accuracy matters (EN 10143 for coated sheet, EN 10131 for cold rolled).
Common metric thicknesses in the market
- Cold rolled and GI: 0.4, 0.5, 0.6, 0.7, 0.8, 1.0, 1.2, 1.5, 2.0 mm
- Hot rolled: 2.0, 2.5, 3.0, 4.0, 5.0, 6.0 mm and up
- Roofing sheets: often quoted as base metal thickness (BMT) 0.4–0.7 mm
Calculate sheet weight
Weight (kg) = length (m) × width (m) × thickness (mm) × 7.85. A 1.25 × 2.5 m sheet at 1.5 mm weighs about 36.8 kg. Use our steel weight calculator.
See our steel sheets range for HR, CR and GI options.