What Tube Gauge Means
Gauge is an old way of naming steel thickness, and tube and sheet use different tables. 14 gauge tube is .083 inch; 14 gauge sheet is .0747. From 11 gauge and heavier, the two all but meet.
Tube Gauge Chart.
Thickness in inches. When a drawing gives a gauge, check which table it means; when in doubt, give the decimal.
| Gauge | Tube wallin | Sheet steelin | Differencein |
|---|---|---|---|
| 14 ga | 0.083 | 0.0747 | +0.0083 |
| 13 ga | 0.095 | 0.0897 | +0.0053 |
| 12 ga | 0.109 | 0.1046 | +0.0044 |
| 11 ga | 0.120 | 0.1196 | 0.0004 |
| 10 ga | 0.134 | 0.1345 | -0.0005 |
| 9 ga | 0.148 | 0.1495 | -0.0015 |
| 8 ga | 0.165 | 0.1644 | +0.0006 |
| 7 ga | 0.180 | 0.1793 | +0.0007 |
| 3/16 in | .188 | – | – |
Tube walls are the nominal values from our size list. Sheet values are the manufacturer's standard gauge for sheet steel.
Reading a Tube Size.
A tube size is written outside by outside by wall. 2 x 2 x .120 and 2 x 2 x 11 ga are the same tube.
Two Tables
Tube wall gauges come from the Birmingham Wire Gauge. Sheet steel uses the Manufacturers' Standard Gauge. The same number means a different thickness, most of all at 14 to 12 gauge.
Fractions
The heaviest walls are usually named as fractions: 1/8 in (.125) and 3/16 in (.188). Both are on our size list, next to 11 and 7 gauge.
Pipe Sizes
Pipe wall is named by schedule, not gauge. Schedule 40 is heavier than Schedule 10 at the same pipe size. See rounds at pipe diameters.
Nominal Wall
The decimal is a nominal wall. A500 and A513 both allow 10% either way on square and rectangular tube, measured at the center of a flat.
Why the Wall Matters.
Weight and strength both climb with wall. A 2 x 2 A500 tube weighs 2.105 lb per foot at .083 wall and 4.327 lb per foot at .188, about twice as much for the same outside size.
A heavier wall is stiffer and carries more load, but it costs more per foot and takes more heat to weld. Often a larger size with a lighter wall is stronger for the same weight. Compare both before you settle on a size.
Square, rectangular and smaller round walls run from .083 to .188 inch (14 gauge to 3/16), with .203 on 2-1/2 in Schedule 40 pipe. Rounds from 4.500 to 8.000 OD run to .300 inch.
Questions.
When a print gives a gauge, ask which table it means, or give the decimal on the quote.
What gauge is .120 wall tube?
11 gauge. At this gauge tube and sheet nearly agree: 11 gauge sheet is .1196 inch.
How thick is 14 gauge steel tube?
.083 inch. 14 gauge sheet steel is thinner, .0747 inch, because sheet uses a different gauge table.
Is 3/16 wall the same as 7 gauge?
Close, but no. 7 gauge tube is .180 inch and 3/16 is .188 inch, so 3/16 is a little heavier.
Is 1/8 inch wall the same as 11 gauge?
No. 1/8 inch is .125 and 11 gauge is .120. Both are on our size list, so name the one on your drawing.
Why is 14 gauge tube thicker than 14 gauge sheet?
Tube gauges follow the Birmingham Wire Gauge and sheet follows the Manufacturers' Standard Gauge. The two tables differ most at the lighter gauges and nearly match from 11 gauge up.
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