Materials
Steel gauge explained, with a thickness chart
Updated August 1, 2026 · 3 minute read · All guides
In short
Steel gauge is a legacy numbering system for sheet thickness where a higher gauge number means thinner steel. It is not a unit and it is not consistent between materials: 16 gauge sheet steel is about 1.52 mm (0.0598 in), while 16 gauge aluminium and 16 gauge stainless are different thicknesses again. For anything that will be quoted, fabricated or ordered, specify thickness in millimetres or decimal inches and treat the gauge number as a label.
Key facts
- Higher gauge number means thinner material. The scale runs backwards from intuition.
- Gauge is not a unit of measurement and differs by material: steel, stainless and aluminium gauges are not interchangeable.
- Standard sheet steel: 10 ga is 3.42 mm, 14 ga is 1.90 mm, 16 ga is 1.52 mm, 20 ga is 0.91 mm.
- Stainless uses a different gauge table again: 16 ga stainless is 1.59 mm, not 1.52 mm.
- Always order and quote in mm or decimal inches. Gauge is a source of expensive misunderstandings.
Why the scale runs backwards
Gauge numbering comes from wire drawing. A wire was pulled through progressively smaller dies, and the gauge number counted the number of draws. More draws meant thinner wire, so a higher number came to mean a thinner product. That logic left wire behind and attached itself to sheet, where it has been quietly causing ordering errors ever since.
The important consequence: gauge is not a unit. It is an index into a table, and there is more than one table.
Sheet steel gauge to thickness
Standard (manufacturers' standard gauge) for uncoated carbon sheet steel:
| Gauge | Inches | Millimetres |
|---|---|---|
| 7 | 0.1793 | 4.55 |
| 8 | 0.1644 | 4.18 |
| 10 | 0.1345 | 3.42 |
| 11 | 0.1196 | 3.04 |
| 12 | 0.1046 | 2.66 |
| 14 | 0.0747 | 1.90 |
| 16 | 0.0598 | 1.52 |
| 18 | 0.0478 | 1.21 |
| 20 | 0.0359 | 0.91 |
| 22 | 0.0299 | 0.76 |
| 24 | 0.0239 | 0.61 |
| 26 | 0.0179 | 0.45 |
Galvanized sheet uses a slightly different table, because the zinc coating adds thickness. A 16 gauge galvanized sheet is nominally 0.0635 in (1.61 mm) rather than 0.0598 in.
Stainless and aluminium are different tables
This is where orders go wrong.
| Gauge | Carbon steel (mm) | Stainless (mm) | Aluminium (mm) |
|---|---|---|---|
| 12 | 2.66 | 2.78 | 2.05 |
| 14 | 1.90 | 1.98 | 1.63 |
| 16 | 1.52 | 1.59 | 1.29 |
| 18 | 1.21 | 1.27 | 1.02 |
| 20 | 0.91 | 0.95 | 0.81 |
A 16 gauge aluminium panel is roughly 15 percent thinner than 16 gauge carbon steel. If a drawing says "16 ga" without naming the material, it has not specified a thickness.
Where gauge shows up in industrial supply
You meet gauge most often in:
- Sheet and plate for fabricated guards, enclosures and covers. Above about 3 mm the trade generally stops using gauge and moves to plate thickness in mm or inches, which is one reason 7 gauge is roughly where the scale runs out of usefulness.
- Tube and pipe wall thickness, where gauge occasionally appears but schedule numbers are the real system.
- Cable tray, ducting and light structural work, where gauge is still the everyday language.
Lifting and rigging products do not use gauge. Chain is specified by nominal diameter and grade, wire rope by diameter and construction, and synthetic slings by rated capacity and ply. If a supplier quotes you a gauge for a lifting product, ask what they actually mean.
How to avoid the expensive version of this mistake
Three habits:
- Quote and order in millimetres or decimal inches. Put the gauge in brackets afterwards if it helps the shop floor.
- Name the material whenever you use a gauge number. "16 ga" is ambiguous; "16 ga carbon steel (1.52 mm)" is not.
- Confirm coating. Galvanized, painted and bare sheet of the same gauge are not the same finished thickness, and on close-tolerance assemblies that matters.
Ordering fabricated items from us
Where we source fabricated steel items to specification, send the thickness in mm or inches, the material and grade, the finish, and a drawing if you have one. We will convert to whatever the producing mill works in and confirm the actual thickness on the quote, rather than passing a gauge number down the chain and hoping everyone reads the same table.