Sheet Gauge to Millimetre Conversion Chart
Standard gauge (Ga) to metric thickness conversion for mild steel, stainless and galvanised sheet, with the sourcing note that matters
Sheet metal gauge is an American convention (US Standard Gauge and the Manufacturers' Standard Gauge) that assigns a number to a thickness, but the number means a different actual thickness depending on the material -- 16 gauge steel is not the same thickness as 16 gauge aluminium. In Egypt, the UAE and Saudi Arabia, most suppliers stock and quote in millimetres, so gauge callouts from older US-influenced drawings or imported equipment specifications need converting before ordering.
This page gives the conversion table for the most common materials and explains why specifying millimetres directly avoids the ambiguity that gauge numbers carry across material types.
Gauge to mm: mild steel and stainless
For mild steel and stainless sheet, the Manufacturers' Standard Gauge applies, and the two materials share the same gauge-to-thickness table since both use the same reference system historically based on weight per square foot. A 16-gauge sheet in either mild steel or 304 stainless is nominally 1.5 mm.
Actual sheet thickness from a mill can vary slightly (typically ±5-10%) from the nominal gauge value, so a critical-tolerance application should always specify the millimetre thickness with a tolerance, not just the gauge number.
| Gauge (Ga) | Mild steel / stainless (mm) | Common use |
|---|---|---|
| 10 Ga | 3.4 mm | Heavy brackets, structural panels |
| 12 Ga | 2.7 mm | Enclosures, structural brackets |
| 14 Ga | 1.9 mm | General enclosures, guarding |
| 16 Ga | 1.5 mm | Standard enclosure panels, brackets |
| 18 Ga | 1.2 mm | Light enclosures, covers |
| 20 Ga | 0.9 mm | Light covers, ducting |
| 22 Ga | 0.8 mm | Thin covers, trim |
Gauge to mm: galvanised sheet
Galvanised steel commonly uses the same Manufacturers' Standard Gauge base thickness as mild steel, but the zinc coating adds a small amount to the finished thickness (typically 0.04-0.06 mm total for a standard Z275 coating), which matters only for very tight-fit applications like nested ducting sections.
Galvanised sheet used in ducting and HVAC work in the region is more often specified directly by DX51D+Z plus a millimetre thickness (0.5, 0.6, 0.8, 1.0, 1.2 mm being common stocked values) than by gauge, since HVAC contractors typically work from metric ductwork standards.
| Gauge (Ga) | Galvanised steel base metal (mm) | Common use |
|---|---|---|
| 24 Ga | 0.7 mm | Light ducting |
| 22 Ga | 0.8 mm | Standard ducting |
| 20 Ga | 0.9 mm | Ducting, brackets |
| 18 Ga | 1.2 mm | Structural ducting, enclosures |
| 16 Ga | 1.5 mm | Heavy ducting, structural panels |
Gauge to mm: aluminium (different system)
Aluminium sheet in the US market sometimes uses the Brown & Sharpe (B&S) gauge, which is a different numbering system entirely from the Manufacturers' Standard Gauge used for steel. This is the most common source of costly ordering mistakes: specifying 16 gauge aluminium expecting 1.5 mm (the steel value) actually gets roughly 1.29 mm, a meaningful difference for a structural or sealing application.
For this reason, aluminium is almost always specified directly in millimetres by suppliers in the region, and gauge numbers on imported drawings referencing aluminium sheet should be treated with caution and converted before ordering.
| Gauge (B&S) | Aluminium (mm) |
|---|---|
| 10 Ga | 2.59 mm |
| 12 Ga | 2.05 mm |
| 14 Ga | 1.63 mm |
| 16 Ga | 1.29 mm |
| 18 Ga | 1.02 mm |
| 20 Ga | 0.81 mm |
Why we recommend specifying millimetres directly
Since the same gauge number means a different thickness depending on whether the material is steel, stainless, galvanised steel or aluminium, and since actual mill tolerance varies the real thickness by several percent either way, gauge alone is not precise enough for a fabrication order. Every quote and drawing processed by CutLinq specifies thickness in millimetres to remove this ambiguity.
If your reference drawing or equipment manual only lists a gauge number, tell us the material along with the gauge and we will confirm the correct millimetre equivalent before quoting, rather than assuming the wrong conversion table.
Design tips
- Always specify thickness in millimetres on drawings submitted for a quote; if you only have a gauge number, state the material as well so the correct conversion table applies.
- Do not assume steel and aluminium gauge tables match; 16 gauge steel (1.5 mm) and 16 gauge aluminium (1.29 mm) differ by more than 14%.
- For sealing or nested-fit applications (ducting, telescoping enclosures), request a millimetre tolerance explicitly, since mill tolerance on gauge-nominal sheet can be ±5-10%.
- When converting an old US-sourced equipment drawing, note whether the aluminium gauge reference used is Brown & Sharpe (most common) before converting.
- Common stocked millimetre thicknesses in the region for mild steel are 1, 1.5, 2, 3, 4, 5, 6, 8, 10 mm; ordering an odd thickness like 2.3 mm may require import and add lead time.
- For HVAC ducting, specify DX51D+Z plus millimetre thickness directly rather than gauge, since most regional contractors and suppliers already work in metric ductwork standards.
- Keep a note on the drawing of which gauge standard (Manufacturers' Standard vs Brown & Sharpe) was used if gauge is referenced at all, to avoid a supplier guessing.
Applications
| Industry | Typical gauge reference | Recommended mm spec |
|---|---|---|
| HVAC and ducting | 22-16 Ga galvanised | 0.8-1.5 mm DX51D+Z |
| Electrical enclosures | 16-12 Ga mild steel/stainless | 1.5-2.7 mm |
| Signage and architecture | 18-14 Ga aluminium | 1.0-1.6 mm |
| Automotive brackets | 14-10 Ga mild steel | 1.9-3.4 mm |
| Kitchen and food equipment | 18-16 Ga stainless | 1.2-1.5 mm |
| Light covers and trim | 22-20 Ga steel/aluminium | 0.8-0.9 mm |
Pricing and lead time
Gauge itself does not affect pricing directly -- the millimetre thickness it converts to does, since thicker sheet costs more per kg of material and takes longer to cut. Ordering a non-standard thickness that only exists as a gauge conversion but is not commonly stocked in mm may require import and add 1-2 weeks to lead time; sticking to common stocked mm values (1, 1.5, 2, 3 mm and similar) keeps standard lead times of 2-5 working days for laser-cut parts.
Frequently asked questions
No. 16 gauge steel and stainless is 1.5 mm; 16 gauge aluminium (Brown & Sharpe system) is 1.29 mm, about 14% thinner. Always confirm the material when converting a gauge number.
Upload a DXF or STEP file with thickness in millimetres, or tell us the gauge and material, and receive a binding quote within 12 hours.