Complete Brown & Sharpe gauge reference chart for aluminum sheet. Instantly look up any gauge number and get the exact thickness in millimetres and decimal inches — gauges 1 through 36.
Enter a gauge number to instantly get thickness in mm and inches, or enter a thickness to find the nearest gauge
Standard Brown & Sharpe (B&S) gauge system — the official gauge scale used for aluminum sheet in North America
| Gauge # | Thickness (inches) | Thickness (mm) | Fraction (approx.) | Category |
|---|
* Based on Brown & Sharpe (B&S) / American Wire Gauge (AWG) standard for aluminum. 1 inch = 25.4 mm. Values may vary slightly by manufacturer — always verify with a micrometer for precision work.
Essential knowledge for fabricators, engineers and buyers working with aluminum sheet
Gauge 7 (0.1443″ / 3.665 mm) is significantly thicker than gauge 30 (0.0100″ / 0.255 mm). The higher the number, the thinner the sheet.
18-gauge aluminum is 0.0403″ (1.024 mm), while 18-gauge steel is 0.0478″ (1.214 mm). Always use material-specific charts — never assume gauges are identical across metals.
The gauge system is a North American convention. Most metric countries specify aluminum thickness directly in millimetres — e.g. "1.5 mm aluminum sheet" rather than a gauge number.
Gauges 16–24 (0.51 mm – 1.29 mm) cover most general-purpose aluminum fabrication including enclosures, panels, HVAC ducts, and automotive trim.
Thick gauges (7–12) are used for structural plates, tooling jigs, and load-bearing brackets where rigidity matters more than weight savings.
Very thin gauges (24–30) are typical for roofing panels, decorative cladding, flashing, and foil-backed insulation applications.
Side-by-side comparison of the same gauge numbers across aluminum and galvanized steel — the differences are significant
| Gauge # | Aluminum (inches) | Aluminum (mm) | Steel (inches) | Steel (mm) | Difference (mm) |
|---|---|---|---|---|---|
| 10 | 0.1019 | 2.588 | 0.1345 | 3.416 | +0.828 |
| 12 | 0.0808 | 2.053 | 0.1046 | 2.657 | +0.604 |
| 14 | 0.0641 | 1.628 | 0.0747 | 1.897 | +0.269 |
| 16 | 0.0508 | 1.291 | 0.0598 | 1.519 | +0.228 |
| 18 | 0.0403 | 1.024 | 0.0478 | 1.214 | +0.190 |
| 20 | 0.0320 | 0.813 | 0.0359 | 0.912 | +0.099 |
| 22 | 0.0253 | 0.643 | 0.0299 | 0.759 | +0.116 |
| 24 | 0.0201 | 0.511 | 0.0239 | 0.607 | +0.096 |
| 26 | 0.0159 | 0.405 | 0.0179 | 0.455 | +0.050 |
| 28 | 0.0126 | 0.321 | 0.0149 | 0.378 | +0.057 |
* Steel values are for galvanized/mild steel (Manufacturers' Standard Gauge). Aluminum uses Brown & Sharpe (AWG). The same gauge number is always thicker in steel than in aluminum.
A simple step-by-step guide to finding and using the right gauge for your project
Locate the gauge number in the left column of the chart. Numbers run from 1 (thickest) to 36 (thinnest) for aluminum sheet.
Read across the row to find the exact thickness in decimal inches (e.g. 0.0403″) and in millimetres (e.g. 1.024 mm) for that gauge.
Always double-check you are using the aluminum gauge chart — the same gauge number gives a different thickness in steel, stainless, or copper.
Gauge charts give nominal values. For precision work, measure the actual sheet with a digital micrometer — manufacturing tolerances can be ±5–8%.
The mathematical relationship behind the Brown & Sharpe gauge system
More free tools for metal fabricators and engineers
Common questions from fabricators, designers and buyers about aluminum sheet gauge thickness