Sheet Metal Gauge Converter
Convert sheet metal gauge to inches and mm, or find the nearest gauge for a thickness, using separate steel, galvanized, stainless and aluminium tables.
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About this toolWhat is the Sheet Metal Gauge Converter?
A gauge number is not a thickness. It is an index into a table, and different metals use different tables, so 16 gauge steel is 0.0598 in, 16 gauge galvanized is 0.0635 in, 16 gauge stainless is 0.0625 in and 16 gauge aluminium is 0.0508 in. Ordering or designing with the wrong table can leave you 20% off. This converter keeps the tables separate and tells you which one each number came from.
Choose gauge to thickness or thickness to gauge, pick the material, and read the result in inches and millimetres with the weight per area. The same gauge number is shown in the other three tables so you can see the difference at a glance, and the full chart below lists every gauge from 0 to 38 side by side with your row highlighted. In reverse mode the tool finds the nearest gauge to a metric thickness and warns you when no gauge in that table is within 0.1 mm.
- Separate verified tables for steel, galvanized, stainless and aluminium
- Gauge to thickness and thickness to nearest gauge
- Inches, millimetres and weight per area
- Same gauge shown in every other table
- Full side-by-side gauge chart with source notes
How to use the Sheet Metal Gauge Converter
- Choose the direction: gauge to thickness, or thickness to the nearest gauge.
- Pick the material table: steel, galvanized, stainless, or aluminium and copper (Brown & Sharpe).
- Select the gauge number, or type a thickness in mm or inches.
- Read the thickness in inches and millimetres, the weight per area and the same gauge in the other tables.
- Scroll the chart for the full table, or copy the result with its source.
Worked examples
16 gauge in four materials
Input
Gauge 16
Output
Steel 0.0598 in (1.519 mm), galvanized 0.0635 in, stainless 0.0625 in, aluminium 0.0508 in (1.290 mm)
The aluminium sheet is 15% thinner than steel with the same number, and 20% thinner than galvanized.
Nearest steel gauge to 1.2 mm
Input
Thickness 1.2 mm, steel table
Output
18 ga, 0.0478 in (1.214 mm), 0.014 mm over
Metric 1.2 mm sheet is the usual substitute for 18 gauge. The steel weighs about 9.53 kg/m².
3 mm stainless
Input
Thickness 3 mm, stainless table
Output
11 ga, 0.125 in (3.175 mm), 0.175 mm over
The nearest stainless gauge is about 6% thicker than 3 mm, so a metric 3 mm sheet is not a straight swap for 11 gauge where thickness matters.
Background and insight
Gauges grew out of wire drawing, where the number counted the passes through successively smaller dies, which is why a higher number is thinner. For sheet steel the US settled on the Manufacturers’ Standard Gauge, which assigns thickness by weight at 41.82 lb per square foot per inch. Each steel thickness here is the nominal weight divided by that constant, so 10 gauge, nominally 5.625 lb/ft², is 0.1345 in. This is the table reproduced in Machinery’s Handbook.
Galvanized sheet uses its own gauge, which is the steel gauge plus a fixed allowance of about 0.0037 in for the zinc. Stainless is normally sold to the older US Standard Gauge of 1893, written into US law at 15 U.S.C. 206, which is why its values look like fractions of an inch (16 gauge is 1/16 in). Aluminium, copper and brass sheet use the Brown & Sharpe gauge, the same series as American Wire Gauge, defined by d = 0.005 x 92^((36 − n)/39) inches in ASTM B258.
Outside North America sheet is ordered in millimetres, and even in the US most mills and laser shops quote decimal thickness. Suppliers also round stainless and aluminium gauges differently, so treat any gauge as nominal and put the decimal thickness on the drawing and the purchase order.
Common use cases
Reading US drawings in metric
Turn the gauge callouts on imported drawings into millimetres for a metric supplier.
Substituting metric sheet
Find the closest metric thickness for a gauge and see how far off it is.
Checking quotes
Make sure a quote for 14 gauge aluminium means 0.0641 in, not the 0.0747 in of 14 gauge steel.
Duct and HVAC work
Look up galvanized gauges used in duct construction standards.
Tips and limitations
- Always state which gauge system you mean, or better, give the decimal thickness.
- Gauge thickness is nominal. Mill tolerances can be ±0.004 in or more on thicker sheet.
- Above about 7 gauge (3/16 in) material is usually called plate and specified in fractions of an inch or millimetres.
- Copper sheet in roofing and flashing is often sold by weight in ounces per square foot, not by gauge.
- The aluminium column follows the Brown & Sharpe formula; some suppliers round these values to three decimals.
Frequently asked questions
How thick is 16 gauge sheet metal in mm?
It depends on the metal: 1.519 mm for steel (0.0598 in), 1.613 mm for galvanized (0.0635 in), 1.588 mm for stainless (0.0625 in) and 1.290 mm for aluminium (0.0508 in).
Why does a higher gauge number mean thinner metal?
Gauge numbers come from wire drawing, where each pass through a smaller die raised the number. Sheet gauges kept the convention, so 24 gauge is much thinner than 10 gauge.
Is stainless steel gauge the same as carbon steel gauge?
No. Carbon steel uses the Manufacturers’ Standard Gauge (16 ga = 0.0598 in) while stainless is normally sold to the US Standard Gauge (16 ga = 0.0625 in). The difference is small but real.
What gauge is 1/8 inch steel?
About 11 gauge: 0.1196 in in the steel table, 0.125 in in the stainless table. In aluminium, 1/8 in is close to 8 gauge (0.1285 in).
What is 10 gauge steel in inches?
0.1345 in (3.416 mm) in the Manufacturers’ Standard Gauge. Galvanized 10 gauge is 0.1382 in and stainless 10 gauge 0.1406 in.
Which gauge system does aluminium use?
The Brown & Sharpe gauge, identical to American Wire Gauge, where each step is a ratio of 92^(1/39), about 1.123. Copper and brass sheet use the same series.
Is there an in-depth guide to the Sheet Metal Gauge Converter?
Yes. “Sheet Metal Gauge Charts Explained: Steel, Galvanized, Stainless, Aluminium” covers the background, how it works, common pitfalls and worked examples. Read the full guide.
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