Gauge is a traditional way of describing sheet metal thickness with a number instead of a measurement. It’s still common on older drawings and in conversation, but it isn’t precise enough for thin-gauge strip. Brown Metals Company stocks, quotes and ships every order by decimal thickness, in inches or millimeters.
Why gauge isn’t enough
There’s more than one gauge chart
Different metals use different gauge systems, and the same gauge number gives a different thickness in each:
- Stainless steel is usually sized by a chart based on the U.S. Standard Gauge.
- Carbon steel, such as 1008 / 1010, uses the Manufacturers’ Standard Gauge.
- Copper alloys, such as beryllium copper, and aluminum use the Brown & Sharpe gauge, also known as American Wire Gauge (AWG).
Example24 gauge = .0250″ stainless · .0239″ carbon steel · .0201″ copper alloy
That’s a spread of almost 25% for one gauge number. Our standard thickness tolerance is about ±5% of the thickness, so ordering by gauge alone can easily land outside the thickness your part needs.
The gauge doesn’t always match the metal
A drawing or purchase order may give a gauge without saying which chart it came from. A stainless part might be dimensioned from a steel chart, or the other way around, and there’s no way for us to tell from the gauge number.
Many thin-gauge sizes have no gauge at all
Sheet metal gauge charts generally stop at about 38 gauge, around .006″. We stock strip as thin as .0005″, and many of our stocked thicknesses, such as .0015″, .0025″ and .0035″, don’t correspond to any gauge.
Higher gauge means thinner
Gauge numbers run backwards: 30 gauge is thinner than 20 gauge. It’s an easy mix-up for newer buyers and another reason we work in decimals.
Gauge to decimal thickness chart
Nominal thickness in inches for gauges in our thickness range (.040″ and thinner). Use this chart to see roughly what a gauge callout means — then confirm the decimal thickness before you order.
Gauge to Decimal Thickness (nominal, inches)
| Gauge | Stainless SteelU.S. Standard | Carbon SteelManufacturers' Standard | Copper AlloysBrown & Sharpe (AWG) |
|---|---|---|---|
| 20 | .0375 | .0359 | .0320 |
| 21 | .0344 | .0329 | .0285 |
| 22 | .0312 | .0299 | .0253 |
| 23 | .0281 | .0269 | .0226 |
| 24 | .0250 | .0239 | .0201 |
| 25 | .0219 | .0209 | .0179 |
| 26 | .0187 | .0179 | .0159 |
| 27 | .0172 | .0164 | .0142 |
| 28 | .0156 | .0149 | .0126 |
| 29 | .0141 | .0135 | .0113 |
| 30 | .0125 | .0120 | .0100 |
| 31 | .0109 | .0105 | .0089 |
| 32 | .0102 | .0097 | .0080 |
| 33 | .0094 | .0090 | .0071 |
| 34 | .0086 | .0082 | .0063 |
| 35 | .0078 | .0075 | .0056 |
| 36 | .0070 | .0067 | .0050 |
| 37 | .0066 | .0064 | .0045 |
| 38 | .0063 | .0060 | .0040 |
Gauge charts from different sources sometimes round these values differently. Treat the chart as a guide, not a specification — the decimal thickness on your drawing or purchase order is what governs.
What to send us instead
Give us the decimal thickness, in inches (for example .025″) or millimeters (for example 0.64 mm), along with the alloy, temper, width and quantity. Our Stock List shows every thickness we stock, and the thickness tolerance article shows the tolerance for each.
If gauge is all you have, use the chart above to find the likely decimal thickness for your alloy, then confirm that thickness with your drawing, purchase order or engineer. Once it’s confirmed, send it through our request for quote form or call (800) 992-5015. We quote from the confirmed decimal thickness, not the gauge number.
This article is educational information only. Always order to the thickness called for by your drawing or purchase order.