Why is 16 gauge steel thicker than 16 gauge aluminium?

Because gauge numbers were historically based on weight per area, not on a fixed thickness, and different metals have different densities. The same gauge number therefore corresponds to different thicknesses in steel, stainless and aluminium. Always work from the actual thickness in inches or millimetres, never from the gauge number alone.

Which gauge thicknesses are most common in fabrication?

For general sheet metal work, 14 to 22 gauge covers most enclosure, ductwork and furniture parts; 10 to 11 gauge shows up in brackets and frames; below 10 gauge you are usually into plate territory, specified in fractions of an inch or millimetres rather than gauge.

Is the tonnage chart in gauge or thickness?

Real tonnage calculations use thickness — millimetres or inches. Gauge is a purchasing and catalogue convention; the tonnage calculator takes thickness directly, and converting from gauge with the wrong metal table is a classic source of under-specified machines.

Does galvanised steel have the same thickness as mild steel at the same gauge?

Essentially yes for the base steel — the zinc coating adds a small amount of thickness per surface, which matters for tight fits but is usually ignored for bending calculations. Stainless, however, is meaningfully heavier per gauge.

What thickness do Europeans mean by 1.5 mm sheet?

Metric sheet is specified directly in millimetres — 0.5, 0.8, 1, 1.5, 2, 3 mm and so on — with no gauge equivalent at all. Most of the world outside North America works this way, which is one reason cross-border quoting mixes units and causes mistakes.

Where does gauge end and plate begin?

Around 3/16 in (roughly 4.8 mm) in common usage: thinner material is sheet and specified by gauge or millimetres, thicker material is plate and specified in fractions or millimetres. Plate bending is a different machine class — see the plate press brake range.

Guide

Sheet metal gauge chart: steel, stainless and aluminium

Gauge is the most misleading number in sheet metal: 16 gauge is one thickness in steel and a noticeably different one in aluminium. These are the reference tables, and the two rules that stop gauge from costing you a scrapped batch.

The two rules

Gauge numbers are not transferable between metals. Use the table for the specific metal, or better, get the thickness from the mill certificate.
Every calculation uses thickness, not gauge. Tonnage, bend allowance, V-opening, minimum flange — all of them work in inches or millimetres.

Steel sheet gauge (mild and galvanised)

Gauge	Inches	Millimetres	Typical use
7	0.1793	4.55	Heavy brackets, structural sheet
8	0.1644	4.18	Frames, heavy enclosures
10	0.1345	3.42	Frames, tray bases
11	0.1196	3.04	Stiffeners, mounting plates
12	0.1046	2.66	Structural parts
14	0.0747	1.90	Enclosure backs, thick panels
16	0.0598	1.52	Enclosure panels, doors
18	0.0478	1.21	Panels, covers, ductwork
20	0.0359	0.91	Covers, trays, light boxes
22	0.0299	0.76	Light boxes, small parts
24	0.0239	0.61	Trim, small parts

Stainless steel gauge

Gauge	Inches	Millimetres
10	0.1406	3.57
12	0.1094	2.78
14	0.0781	1.98
16	0.0625	1.59
18	0.0500	1.27
20	0.0375	0.95
22	0.0312	0.79

Note the pattern: at the same gauge number, stainless is thicker than steel. A shop that converts a 16 gauge stainless part to “16 gauge mild steel” without adjusting thickness is bending thinner material than the part drawing intended.

Aluminium gauge

Gauge	Inches	Millimetres
10	0.1019	2.59
12	0.0808	2.05
14	0.0641	1.63
16	0.0508	1.29
18	0.0403	1.02
20	0.0320	0.81
22	0.0253	0.64

Metric sheet, the way most of the world buys it

European and Asian suppliers specify thickness directly: 0.5, 0.6, 0.8, 1.0, 1.2, 1.5, 2.0, 2.5, 3.0 mm are the common steps, with plate at 4 mm and above. If you are quoting against a European drawing in millimetres with a US gauge chart in hand, convert once, at the start, and write the millimetre thickness on the job ticket.

Using the tables with the calculators

Tonnage: take the thickness from the table for your metal and run it through the tonnage calculator.
V-opening: the V-die selector needs thickness, not gauge.
Bend allowance: the bend allowance calculator works from thickness, inside radius and K-factor — see the K-factor guide.

And when in doubt, ask for the mill certificate. Thickness on paper is an assumption; thickness on a certificate is a fact you can bend to.

Still not sure what your power will support?

Tell us your supply voltage, available breaker size and the thickest material you need to bend. We will tell you straight whether single phase will do it.

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