Instantly convert sheet metal thickness in mm or inches to gauge number. Supports sheet steel, stainless steel, aluminium, copper, galvanised iron, SWG and BWG gauge standards.
Enter thickness in mm or inches, select material standard and instantly find the matching gauge number with nearest values.
Follow these simple steps to find the correct gauge number for any sheet metal thickness in seconds
Select mm if your drawing or caliper measurement is in metric. Select Inches if you have an imperial dimension from a US or UK supplier specification sheet.
Type your measured or specified thickness. For example enter 1.5 for 1.5 mm sheet, or 0.060 for 60 thou (60 thousandths of an inch). Results update live as you type.
Gauge numbers differ by material — 16 gauge steel ≠ 16 gauge aluminium. Select the correct standard: Sheet Steel (USSG), Stainless Steel, Aluminium, Copper/Brass (BWG) or SWG.
The converter finds the closest matching gauge number to your input thickness. It also shows the exact standard thickness in mm and inches, plus the difference from your input value.
The Next Gauge result shows the adjacent gauge number. Use this when your thickness falls between two gauges — helping you decide whether to go one gauge thicker or thinner for your application.
Why gauge numbers differ by material and which standard to use for your application
The most common gauge standard for mild (carbon) steel sheet and plate in the USA and internationally. Based on weight per square foot, not a direct thickness formula. Defined under ASTM A480. Example: 18 gauge steel = 1.214 mm (0.0478 in).
Stainless steel uses a separate gauge table because it is denser than mild steel. The same gauge number gives a slightly different thickness. Example: 16 gauge stainless = 1.588 mm (0.0625 in) vs. 16 gauge steel = 1.519 mm (0.0598 in). Reference: ASTM A240.
Aluminium sheet gauge follows the Brown & Sharpe (B&S) wire gauge system, also known as AWG for non-ferrous metals. Aluminium gauge numbers correspond to thinner sheets than steel at the same number. Example: 16 gauge aluminium = 1.290 mm (0.0508 in). Reference: ASTM B209.
BWG (Birmingham Wire Gauge) is used for copper, brass and non-ferrous sheet and tube in the UK and many export markets. It is a legacy standard but still widely referenced in plumbing, electrical and marine engineering. Example: 16 BWG = 1.651 mm (0.065 in). Reference: CDA Copper Standards.
SWG (Standard Wire Gauge) is a British imperial standard used for steel, copper and aluminium wire and sheet, still widely used in UK, India, Pakistan and Commonwealth countries. Example: 16 SWG = 1.626 mm (0.064 in). Defined in BS 3737.
Gauge systems originated from wire drawing — the number of times wire was drawn through a die. More draws = thinner wire = higher gauge number. This is why higher gauge = thinner material across all systems. A 22 gauge sheet is always thinner than a 14 gauge sheet regardless of material.
Full gauge conversion table for sheet steel, stainless steel and aluminium per ASTM standards 2026
| Gauge # | Steel (mm) | Steel (in) | Stainless (mm) | Stainless (in) | Aluminium (mm) | Aluminium (in) |
|---|---|---|---|---|---|---|
| 3 | 6.073 | .2391 | 6.350 | .2500 | 5.827 | .2294 |
| 4 | 5.695 | .2242 | 5.954 | .2344 | 5.189 | .2043 |
| 5 | 5.314 | .2092 | 5.556 | .2187 | 4.621 | .1819 |
| 6 | 4.935 | .1943 | 5.159 | .2031 | 4.115 | .1620 |
| 7 | 4.554 | .1793 | 4.762 | .1875 | 3.665 | .1443 |
| 8 | 4.175 | .1644 | 4.366 | .1719 | 3.264 | .1285 |
| 9 | 3.797 | .1495 | 3.969 | .1562 | 2.906 | .1144 |
| 10 | 3.416 | .1345 | 3.572 | .1406 | 2.588 | .1019 |
| 11 | 3.038 | .1196 | 3.175 | .1250 | 2.305 | .0907 |
| 12 | 2.656 | .1046 | 2.778 | .1094 | 2.053 | .0808 |
| 13 | 2.278 | .0897 | 2.381 | .0937 | 1.828 | .0720 |
| 14 | 1.897 | .0747 | 1.984 | .0781 | 1.628 | .0641 |
| 15 | 1.709 | .0673 | 1.786 | .0703 | 1.450 | .0571 |
| 16 | 1.519 | .0598 | 1.588 | .0625 | 1.290 | .0508 |
| 17 | 1.367 | .0538 | 1.429 | .0562 | 1.151 | .0453 |
| 18 | 1.214 | .0478 | 1.270 | .0500 | 1.024 | .0403 |
| 19 | 1.062 | .0418 | 1.111 | .0437 | 0.912 | .0359 |
| 20 | 0.911 | .0359 | 0.952 | .0375 | 0.813 | .0320 |
| 21 | 0.836 | .0329 | 0.873 | .0344 | 0.724 | .0285 |
| 22 | 0.759 | .0299 | 0.794 | .0312 | 0.643 | .0253 |
| 23 | 0.683 | .0269 | 0.714 | .0281 | 0.574 | .0226 |
| 24 | 0.607 | .0239 | 0.635 | .0250 | 0.511 | .0201 |
| 25 | 0.531 | .0209 | 0.556 | .0219 | 0.455 | .0179 |
| 26 | 0.454 | .0179 | 0.476 | .0187 | 0.404 | .0159 |
| 27 | 0.417 | .0164 | 0.437 | .0172 | 0.361 | .0142 |
| 28 | 0.378 | .0149 | 0.397 | .0156 | 0.320 | .0126 |
| 29 | 0.343 | .0135 | 0.358 | .0141 | 0.287 | .0113 |
| 30 | 0.305 | .0120 | 0.318 | .0125 | 0.254 | .0100 |
* Based on ASTM A1008 (steel), ASTM A240 (stainless) and ASTM B209 (aluminium). Tolerances per respective standards apply.
Standard Wire Gauge (SWG) and Birmingham Wire Gauge (BWG) conversion table widely used in UK, India, Pakistan and Commonwealth countries
| Gauge # | SWG (mm) | SWG (in) | BWG (mm) | BWG (in) | Common Application |
|---|---|---|---|---|---|
| 4 | 5.893 | .232 | 6.045 | .238 | Heavy structural plate |
| 6 | 4.877 | .192 | 4.572 | .180 | Heavy sheet fabrication |
| 8 | 4.064 | .160 | 4.191 | .165 | Floor plate, tank base |
| 10 | 3.251 | .128 | 3.404 | .134 | Structural roofing |
| 12 | 2.642 | .104 | 2.769 | .109 | General fabrication |
| 14 | 2.032 | .080 | 2.108 | .083 | Duct work, enclosures |
| 16 | 1.626 | .064 | 1.651 | .065 | Roofing, automotive |
| 18 | 1.219 | .048 | 1.245 | .049 | Appliances, HVAC |
| 20 | 0.914 | .036 | 0.889 | .035 | Signage, light fabrication |
| 22 | 0.711 | .028 | 0.711 | .028 | Electrical enclosures |
| 24 | 0.559 | .022 | 0.559 | .022 | Heating elements, foil |
| 26 | 0.457 | .018 | 0.457 | .018 | Copper roofing sheet |
| 28 | 0.376 | .0148 | 0.381 | .015 | Fine sheet, shim stock |
| 30 | 0.305 | .012 | 0.305 | .012 | Wire, thin foil |
| 32 | 0.274 | .0108 | 0.254 | .010 | Fine wire, electronics |
| 34 | 0.234 | .0092 | 0.203 | .008 | Precision foil |
| 36 | 0.193 | .0076 | 0.165 | .0065 | Ultra-thin applications |
* SWG per BS 3737 (British Standards Institution). BWG is the Birmingham Wire Gauge standard used widely in tube and pipe specifications. Both remain in active use in 2026 for legacy and Commonwealth market applications.
How the same gauge number gives different thicknesses across material standards — a critical fact for engineers and fabricators
| Gauge # | Steel USSG (mm) | Stainless USS (mm) | Aluminium (mm) | SWG (mm) | BWG (mm) |
|---|---|---|---|---|---|
| 10 | 3.416 | 3.572 | 2.588 | 3.251 | 3.404 |
| 12 | 2.656 | 2.778 | 2.053 | 2.642 | 2.769 |
| 14 | 1.897 | 1.984 | 1.628 | 2.032 | 2.108 |
| 16 | 1.519 | 1.588 | 1.290 | 1.626 | 1.651 |
| 18 | 1.214 | 1.270 | 1.024 | 1.219 | 1.245 |
| 20 | 0.911 | 0.952 | 0.813 | 0.914 | 0.889 |
| 22 | 0.759 | 0.794 | 0.643 | 0.711 | 0.711 |
| 24 | 0.607 | 0.635 | 0.511 | 0.559 | 0.559 |
* Always specify both gauge number AND material standard (e.g. "18 gauge stainless steel" not just "18 gauge") to avoid costly ordering errors. Sources: Metal Supermarkets, ASTM A1008, ASTM A240, ASTM B209, BS 3737.
Real-world industries and applications where knowing the exact mm thickness for a gauge number is critical
Modern engineering drawings specify thickness in mm per ISO standards. When sourcing sheet metal quoted in gauge, fabricators must convert accurately to verify the correct material is ordered. A one-gauge error on structural steel can be a costly and dangerous mistake.
Automotive body panels, chassis members and repair panels are often specified in gauge in the USA and UK. Body shops and panel beaters need fast, accurate gauge-to-mm conversion to match OEM specifications and select the correct steel grade and temper.
Galvanised steel roofing sheets (26, 28, 30 gauge) and aluminium cladding panels are widely specified in gauge in construction markets. Architects, quantity surveyors and contractors use gauge conversion to check dead load calculations and wind uplift resistance.
Electrical enclosures, switchgear panels and earthing strips are specified in SWG or steel gauge in many Commonwealth countries. Electrical engineers and panel builders need mm equivalents to verify IP ratings, earthing conductor sizing and structural rigidity.
Stainless steel kitchen equipment, food processing machinery and catering sinks are specified in stainless gauge (USS). Fabricators must use the stainless gauge table — not the steel table — to get the correct thickness in mm or inches for hygienic surface finish compliance.
Marine plate, deck sheeting and copper-nickel pipe are still quoted in BWG or SWG gauge in many shipyards. Marine engineers and surveyors rely on accurate gauge conversion to verify plate thickness against classification society rules (Lloyd's, DNV, ABS).
Best practices used by engineers, fabricators and procurement teams to avoid costly gauge errors
The single biggest source of gauge errors is specifying gauge without material. "16 gauge" means 1.519 mm in steel, 1.588 mm in stainless and 1.290 mm in aluminium. Always write "16 gauge mild steel" or "16 gauge 304 stainless" on every drawing and purchase order.
Physical sheet metal gauge tools (fan gauges) are useful on the shop floor but can be misleading if used on the wrong material standard. Always verify with a calibrated digital micrometer for critical thickness checks. A good micrometer reads to ±0.001 mm accuracy.
ASTM and BS standards allow thickness tolerances of ±5–10% depending on sheet width and gauge. Always request a mill test certificate for structural applications and verify the actual measured thickness falls within the tolerance band for your specified gauge.
USA uses USSG (steel gauge) and AWG (aluminium). UK, India and Pakistan predominantly use SWG. Europe works in mm only with no gauge system. Australia uses both mm and AWG. When importing or exporting, always confirm which gauge standard the supplier is quoting before ordering.
This counterintuitive rule catches out students and engineers new to fabrication. Gauge 28 (0.378 mm steel) is much thinner than gauge 10 (3.416 mm steel). Think of it as the number of times the wire was drawn — more draws = thinner = higher gauge number.
Once you know the exact thickness in mm, use a weight calculator to get kg/m² for procurement. For example 18 gauge mild steel (1.214 mm) × 7.85 g/cm³ = 9.53 kg/m². Use our MS Sheet Weight Calculator for instant total sheet weight and tonnage.
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