Sheet Metal Gauge Chart — Gauge to mm Conversion
Convert sheet metal gauge to millimetres for standard steel, galvanised, stainless and aluminium — each uses a different gauge standard, so the same number is a different thickness. Highlight your material, see the nearest metric sheet we stock, and download the whole reference (with a bend-allowance table) as a free PDF.
Sheet Metal Gauge Chart
Gauge → mm for steel, galvanised, stainless & aluminium — plus the nearest sheet we stock.
| Gauge | Standard Steel Mfrs. Standard Gauge | Galvanised incl. zinc coat | Stainless stainless gauge | Aluminium Brown & Sharpe | Nearest JDL stock metric, mm |
|---|---|---|---|---|---|
| 3 ga | 6.073 | — | — | 5.827 | 6.0 mm |
| 4 ga | 5.695 | — | — | 5.189 | 6.0 mm |
| 5 ga | 5.314 | — | — | 4.620 | 5.0 mm |
| 6 ga | 4.935 | — | — | 4.115 | 5.0 mm |
| 7 ga | 4.554 | — | 4.76 | 3.665 | 5.0 mm |
| 8 ga | 4.176 | 4.270 | 4.37 | 3.264 | 4.0 mm |
| 9 ga | 3.797 | 3.891 | — | 2.906 | 4.0 mm |
| 10 ga | 3.416 | 3.510 | 3.57 | 2.588 | 3.0 mm |
| 11 ga | 3.038 | 3.132 | 3.18 | 2.304 | 3.0 mm |
| 12 ga | 2.657 | 2.753 | 2.78 | 2.052 | 3.0 mm |
| 13 ga | 2.278 | 2.372 | 2.40 | 1.829 | 2.0 mm |
| 14 ga | 1.897 | 1.994 | 1.98 | 1.628 | 2.0 mm |
| 15 ga | 1.709 | 1.803 | — | 1.450 | 1.5 mm |
| 16 ga | 1.519 | 1.613 | 1.59 | 1.290 | 1.5 mm |
| 17 ga | 1.367 | 1.461 | — | 1.151 | 1.5 mm |
| 18 ga | 1.214 | 1.311 | 1.27 | 1.024 | 1.0 mm |
| 19 ga | 1.062 | 1.158 | — | 0.912 | 1.0 mm |
| 20 ga | 0.912 | 1.006 | 0.95 | 0.813 | <1.0 (on request) |
| 21 ga | 0.836 | 0.930 | — | 0.724 | <1.0 (on request) |
| 22 ga | 0.759 | 0.853 | 0.79 | 0.643 | <1.0 (on request) |
| 24 ga | 0.607 | 0.701 | 0.64 | 0.511 | <1.0 (on request) |
| 26 ga | 0.455 | 0.551 | 0.48 | 0.404 | <1.0 (on request) |
All thicknesses in mm. Gauge is material-specific — “18 gauge” steel (1.21mm) is not the same as 18 gauge aluminium (1.02mm). Steel uses the Manufacturers' Standard Gauge, aluminium/brass/copper use Brown & Sharpe. “—” means that gauge isn't part of the material's standard. JDL is metric — we cut sheet by mm, so the last column shows the closest stocked sheet to each gauge.
90° Bend Allowance & Deduction — Mild Steel
Air bend, inside radius = material thickness, using the same K-factor our quoting engine assumes. Flat length = leg A + leg B + BA (or − BD if you work from outside dims).
| Thickness | Inside radius | K-factor | Bend allowance | Bend deduction |
|---|---|---|---|---|
| 1.0 mm | 1.0 mm | 0.43 | 2.25 mm | 1.75 mm |
| 1.5 mm | 1.5 mm | 0.43 | 3.37 mm | 2.63 mm |
| 2.0 mm | 2.0 mm | 0.43 | 4.49 mm | 3.51 mm |
| 3.0 mm | 3.0 mm | 0.43 | 6.74 mm | 5.26 mm |
| 4.0 mm | 4.0 mm | 0.43 | 8.98 mm | 7.02 mm |
| 5.0 mm | 5.0 mm | 0.43 | 11.23 mm | 8.77 mm |
| 6.0 mm | 6.0 mm | 0.43 | 13.48 mm | 10.52 mm |
Need a different angle, radius or material? The interactive K-factor calculator works it out for any combination — or reverse-engineers the K-factor from a test bend.
Designing in gauge? Send us your DXF or STEP and we'll cut and fold it in the nearest metric thickness — instant price, no account needed.
Get an Instant Quote →How sheet metal gauge works
Gauge is a legacy numbering system for sheet thickness. The key quirk catches people out constantly: a higher gauge number means thinner metal. 11 gauge steel is about 3mm; 20 gauge steel is under 1mm. The system descends from wire-drawing, where the gauge counted how many times the wire was pulled through a die.
Because gauge is just a number, it only means something once you also know the material. That is why the chart above has separate columns — and why, on a drawing, you should always write the material next to the gauge (e.g. “16 ga stainless”) or, ideally, just give the thickness in millimetres.
The four gauge standards
- •Standard steel — Manufacturers' Standard Gauge (MSG). The reference for hot- and cold-rolled mild steel sheet. 16 ga = 1.52mm.
- •Galvanised steel. Same base as MSG plus the zinc coating, so a galvanised gauge is slightly thicker than the same gauge in bare steel.
- •Stainless steel. Uses its own gauge standard. 18 ga stainless is exactly 0.050″ (1.27mm) — close to, but not the same as, steel.
- •Aluminium, brass & copper — Brown & Sharpe (B&S). A different progression entirely. 16 ga aluminium is just 1.29mm, noticeably thinner than 16 ga steel.
Gauge vs metric in Australia
Australian steel suppliers sell sheet by metric thickness — 1.0, 1.2, 1.5, 2, 3, 4, 5, 6, 8, 10, 12 and 16mm are the common stocked sizes. Gauge numbers rarely land exactly on these, which is exactly why the chart shows a “Nearest JDL stock” column: it tells you which sheet we would actually cut your part from.
If your design is dimensioned in gauge, you do not need to convert anything before ordering — send the file as-is and we will match it to the nearest stocked thickness, or quote the exact mm if it matters to your fit.
Designing the bends too?
Once you have the thickness, the next question is usually the flat pattern. The downloadable chart includes a 90° bend-allowance and bend-deduction table, and our free calculator works out the flat length for any angle, radius and material — or reverse-engineers the K-factor from a test bend.
Open the K-Factor & Bend CalculatorNeed sheet metal parts cut?
Upload your DXF or STEP file and get an instant price in seconds — laser cutting, press-brake bending and finishing in one Australian-made order. No account, no minimum.
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