01Why one gauge number gives two thicknesses
Gauge is a numbered series inherited from wire drawing, not a measurement. Each metal got its own table because each was drawn through different rolls, and the tables were standardised separately. The result is that “16 gauge” is only a complete specification if you also say which metal.
| Gauge | Stainless steel | Galvanised / mild steel | Birmingham (tube) |
|---|---|---|---|
| 14 | 1.984 mm | 1.897 mm | 2.032 mm |
| 16 | 1.588 mm | 1.518 mm | 1.651 mm |
| 18 | 1.270 mm | 1.214 mm | 1.245 mm |
| 20 | 0.953 mm | 0.912 mm | 0.889 mm |
| 22 | 0.794 mm | 0.758 mm | 0.711 mm |
| 24 | 0.635 mm | 0.607 mm | 0.559 mm |
If a drawing says “16 ga” and nothing else, the question to ask is which of those three tables is meant. The difference between the stainless and the Birmingham column at 16 gauge is 0.063 mm — thin enough to be invisible in a section drawing and thick enough to matter in a weld.
02Convert it
The converter below uses the stainless table for the gauge series, and straight arithmetic for millimetres to inches. It exists because most of the searches that land here are one conversion away from an answer.
Gauge tables: US standard gauge for stainless sheet and for galvanised sheet. Rows outside 8–29 gauge are not defined in the series.
03Plate has no gauge number
This is the part that matters most on a countertop site. The gauge series stops being useful above about 7 mm, and the plate we cut — 5, 6, 8 and 10 mm — is specified in millimetres by everyone, including the mills.
| Plate | Inches | Nearest gauge | Comment |
|---|---|---|---|
| 5 mm | 0.197" | ≈ 4 ga | Heavier than any common sheet gauge |
| 6 mm | 0.236" | ≈ 3 ga | The domestic default |
| 8 mm | 0.315" | ≈ 2 ga | Islands, bars, pass counters |
| 10 mm | 0.394" | ≈ 0 ga | Beyond the series — mill plate |
So when a specification says “16 gauge stainless”, it is describing a 1.588 mm skin over a substrate. When it says “6 mm plate”, it is describing solid material with nothing underneath. Those are different products, and confusing them is the most expensive unit error in this trade.
What plate thickness to choose · Technical data index · Send a drawing
04From thickness to weight, and why it decides the frame
Weight is thickness multiplied by density, and density for 304 is 7.93 kg/dm³. That makes the arithmetic trivial and the consequence large: a 10 mm top is 79.3 kg/m² against 39.7 kg/m² for 5 mm, so the same benchtop more than doubles in mass without changing one dimension on the plan.
That mass is what the carcass, the fixings and two people carrying it have to survive. It is also what makes the difference between a top that can be lifted into place with suction cups and one that needs a lifter, and it is why we ask for the frame in scope on anything over 8 mm.
| Thickness | Weight / m² | Stiffness | Usual job |
|---|---|---|---|
| 5 mm | 39.7 kg | Lowest — needs support or a fold | Volume joinery, fully supported |
| 6 mm | 47.6 kg | Standard | Domestic kitchen, folded front edge |
| 8 mm | 63.4 kg | High | Islands, bars, pass counters |
| 10 mm | 79.3 kg | Highest | Heavy commercial, deliberate slab edge |
Thickness is not a grade question. 304 or 316L is chosen from what touches the surface; 5, 6, 8 or 10 mm is chosen from span, load and how the edge should read. The tolerance we hold is ±0.05 mm at a machined edge regardless of which of the four you pick. On delivery: our lead time is 15 working days from a confirmed drawing, parts are cut, machined, inspected and packed in one building, and packing is on-edge with the edges protected because plate this heavy damages itself in transit if it is stacked flat. The inspection sheet ships with the parts, and that sheet — not a photograph — is what the warranty is settled against.
How thickness changes the bench height · Workbenches and frames · Send a drawing