How thick is 16 gauge steel?

0.0625 in (1/16 in) in the 1893 US Standard Gauge, 0.0613 in at steel density, and 0.0598 in on supplier charts using the Manufacturers Standard Gauge. Galvanized 16 gauge is 0.0635 in on those charts.

How thick is 14 gauge steel?

0.078125 in (5/64 in) in the US Standard Gauge, 0.0766 in at steel density and 0.0747 in on supplier charts. 14 AWG aluminum is 0.0641 in.

How thick is 18 gauge steel?

0.05 in (1/20 in) in the US Standard Gauge, 0.0490 in at steel density and 0.0478 in on supplier charts.

How thick is 20 gauge steel?

0.0375 in (3/80 in) in the US Standard Gauge, 0.0368 in at steel density and 0.0359 in on supplier charts.

How thick is 22 gauge?

0.03125 in (1/32 in) in the US Standard Gauge and 0.0299 in on supplier charts. IRC Table R703.8.4(1) uses 0.0299 in and calls it 22 U.S. gage.

How thick is 26 gauge metal?

0.01875 in in the US Standard Gauge and 0.0179 in on supplier charts. The IRC writes No. 26 as 0.019 in for flashing (R903.2.1) and 0.0187 in elsewhere (R1005.8).

Is a higher gauge thicker or thinner?

Thinner. In every gauge on this page a larger number is a thinner sheet or wire: 10 gauge steel is 0.1406 in in the US Standard Gauge and 20 gauge is 0.0375 in.

What gauge is 1/8 inch?

11 gauge in the US Standard Gauge is exactly 1/8 in (0.125 in). On supplier charts 11 gauge is 0.1196 in, and 8 AWG aluminum is 0.1285 in.

How do I convert gauge to mm?

Multiply the inch thickness by 25.4. 16 gauge US Standard Gauge is 1.59 mm, 0.0598 in supplier gauge is 1.52 mm, and 16 AWG is 1.29 mm.

Home › Structural › Gauge Size Chart

Gauge Size Chart

15 U.S.C. 206 (1893), NBS Circulars 391 and 31, IRC 2021

16 gauge steel is 0.0625 in in the federal law that created the gauge, 0.0598 in on most supplier charts, 0.0635 in when galvanized, 0.0575 in in one section of the building code, and 0.0508 in if it is aluminum. None of those is wrong; they are different gauges sharing a number. The chart below puts them side by side for every gauge, from the 1893 law, the Bureau of Standards circulars and the IRC, and the lookup does the same for one number.

Look up a gauge

Gauge number

One gauge number, read in every system that uses it.

Specification summary

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Worked example

16 gauge, read in each system.

The 1893 law. 16 gauge is 40 oz per sq ft, 2.5 lb, written as 1/16 in or 0.0625 in on a wrought iron basis of 40 lb per sq ft per inch.
Steel. NBS Circular 391 notes steel is 2% heavier, 40.80 lb per sq ft per inch: 2.5 ÷ 40.80 = 0.0613 in.
Supplier charts. The Manufacturers Standard Gauge uses 41.82: 2.5 ÷ 41.82 = 0.0598 in.
Galvanized. Circular 391 adds 2.5 oz: 42.5 oz is 2.656 lb, and on the supplier basis 0.0635 in.
Aluminum. Nonferrous sheet uses the American wire gage: 16 AWG is 0.0508 in.

From 0.0508 to 0.0635 in, the same number covers a 25% range. Ask for the decimal.

The formula

Sheet steel gauges are weight gauges. Thickness is the weight divided by a density figure, and the figure is where the systems part:

thickness (in) = weight (lb per sq ft) ÷ 40.00, 40.80 or 41.82

40.00: wrought iron, the basis of the 1893 law's printed thicknesses
40.80: steel, NBS Circular 391
41.82: the Manufacturers Standard Gauge on supplier charts
AWG: diameter = 0.005 × 92^((36 − n) ÷ 39) in, the law in NBS Circular 31

Galvanized sheet gauge is the US Standard Gauge weight plus 2.5 oz per sq ft, whatever the coating.

Where the numbers come from

The sheet steel gauge is federal law: 15 U.S.C. 206, the Act of March 3, 1893, which defines each gauge by ounces per square foot and prints approximate thicknesses in fractions, decimals and millimeters. NBS Circular 391 (1931) reprints it, adds the steel-density column, and gives the galvanized sheet gage in its Table 7. Each of the circular's 27 galvanized weights was checked against its own rule, the law's weight plus 2.5 oz, and all match.

The supplier column is labeled as such. The Manufacturers Standard Gauge is what steel suppliers print; Welders Supply's 2026 chart gives 0.0598 in for 16 gauge and names 41.82 lb per sq ft per inch as its basis. No federal or standards document defining it was found, so this page shows it as a convention and computes it from that one figure; it reproduces all ten of that chart's values checked here. The AWG is NBS Circular 31's geometric law, which Circular 391 says covers copper, aluminum and nonferrous sheet. The IRC figures were read from its sections on 2026-10-02.

Sheet metal gauge chart

Gauge to thickness, inches unless noted. US Standard Gauge from 15 U.S.C. 206; steel at 40.80 from NBS Circular 391; supplier at 41.82; galvanized weight from NBS C391 Table 7; AWG from NBS Circular 31
Gauge	USSG fraction	USSG, in	USSG, mm	Steel at 40.80	Supplier at 41.82	Galvanized, lb per sq ft	AWG (aluminum), in
0000 (4/0 AWG)	13/32	0.40625	10.32	0.3983	0.3886	-	0.4600
000 (3/0 AWG)	3/8	0.375	9.53	0.3676	0.3587	-	0.4096
00 (2/0 AWG)	11/32	0.34375	8.73	0.3370	0.3288	-	0.3648
0 (1/0 AWG)	5/16	0.3125	7.94	0.3064	0.2989	-	0.3249
1	9/32	0.28125	7.14	0.2757	0.2690	-	0.2893
2	17/64	0.265625	6.75	0.2604	0.2541	-	0.2576
3	1/4	0.25	6.35	0.2451	0.2391	-	0.2294
4	15/64	0.234375	5.95	0.2298	0.2242	-	0.2043
5	7/32	0.21875	5.56	0.2145	0.2092	-	0.1819
6	13/64	0.203125	5.16	0.1991	0.1943	-	0.1620
7	3/16	0.1875	4.76	0.1838	0.1793	-	0.1443
8	11/64	0.171875	4.37	0.1685	0.1644	7.031	0.1285
9	5/32	0.15625	3.97	0.1532	0.1495	6.406	0.1144
10	9/64	0.140625	3.57	0.1379	0.1345	5.781	0.1019
11	1/8	0.125	3.17	0.1225	0.1196	5.156	0.0907
12	7/64	0.109375	2.78	0.1072	0.1046	4.531	0.0808
13	3/32	0.09375	2.38	0.0919	0.0897	3.906	0.0720
14	5/64	0.078125	1.98	0.0766	0.0747	3.281	0.0641
15	9/128	0.0703125	1.79	0.0689	0.0673	2.969	0.0571
16	1/16	0.0625	1.59	0.0613	0.0598	2.656	0.0508
17	9/160	0.05625	1.43	0.0551	0.0538	2.406	0.0453
18	1/20	0.05	1.27	0.0490	0.0478	2.156	0.0403
19	7/160	0.04375	1.11	0.0429	0.0418	1.906	0.0359
20	3/80	0.0375	0.95	0.0368	0.0359	1.656	0.0320
21	11/320	0.034375	0.87	0.0337	0.0329	1.531	0.0285
22	1/32	0.03125	0.79	0.0306	0.0299	1.406	0.0253
23	9/320	0.028125	0.71	0.0276	0.0269	1.281	0.0226
24	1/40	0.025	0.64	0.0245	0.0239	1.156	0.0201
25	7/320	0.021875	0.56	0.0214	0.0209	1.031	0.0179
26	3/160	0.01875	0.48	0.0184	0.0179	0.906	0.0159
27	11/640	0.0171875	0.44	0.0169	0.0164	0.844	0.0142
28	1/64	0.015625	0.40	0.0153	0.0149	0.781	0.0126
29	9/640	0.0140625	0.36	0.0138	0.0135	0.719	0.0113
30	1/80	0.0125	0.32	0.0123	0.0120	0.656	0.0100
31	7/640	0.0109375	0.28	0.0107	0.0105	0.594	0.0089
32	13/1280	0.01015625	0.26	0.0100	0.0097	0.562	0.0080
33	3/320	0.009375	0.24	0.0092	0.0090	0.531	0.0071
34	11/1280	0.00859375	0.22	0.0084	0.0082	0.500	0.0063
35	5/640	0.0078125	0.20	0.0077	0.0075	-	0.0056
36	9/1280	0.00703125	0.18	0.0069	0.0067	-	0.0050
37	17/2560	0.006640625	0.17	0.0065	0.0064	-	0.0045
38	1/160	0.00625	0.16	0.0061	0.0060	-	0.0040

The law runs on to No. 38 and starts at No. 0000000 (1/2 in); the three heaviest numbers are left off the chart but are in the lookup. A lower number is always thicker.

The building code does not agree with itself

The IRC mostly writes sheet metal as a decimal with the gauge in brackets. Read side by side, the brackets do not line up:

Gauge and thickness pairs printed in IRC 2021
IRC wording	Section	1893 law, in	Supplier chart, in
0.019 in (No. 26 galvanized sheet)	R903.2.1	0.01875	0.0179; 0.0217 galvanized
No. 26 gage [0.019 in]	R905.7.6, R905.8.8	0.01875	0.0179
0.0187 in (No. 26 gage)	R1005.8	0.01875	0.0179
No. 26 gage (0.48 mm, 0.0189 in)	R302.5.2	0.01875	0.0179
0.0236 in (No. 24 gage) galvanized	Table M1306.2	0.025	0.0276 galvanized
22 U.S. gage (0.0299 in)	Table R703.8.4(1)	0.03125	0.0299
0.0575 in (No. 16 gage)	M1308.2.3	0.0625	0.0598
9 gage [0.148 in] wire	R606.6.4.1.2, R703.8.4.1	-	-
9 gauge (0.144 in) wire	R703.8.3.2	-	-

Three things stand out. No. 26 appears at four thicknesses, all close to the law's 0.01875 in and none at the supplier chart's 0.0179. The code calls 0.0299 in "22 U.S. gage", but that is the supplier figure: the US Standard Gauge in the 1893 law is 0.03125 in. And 9 gauge wire is 0.148 in in two sections and 0.144 in in a third. Duct Table M1601.1.1 avoids the problem by listing only decimals, 0.013 to 0.024 in for galvanized steel.

Wire and nail gauge

Steel wire and nails use a third scale, again with the same numbers. The Wood Handbook prints it beside each nail, and the IRC prints a few pairs:

Steel wire gauge and diameter, Wood Handbook Tables 8-1 and 8-2 (WH) and IRC 2021
Gauge	Diameter, in	Where it is printed
2	0.262	WH 8-1, 60d common
3	0.244	WH 8-1, 50d common
4	0.225	WH 8-1, 40d common
5	0.207	WH 8-1, 30d common
6	0.192	WH 8-1, 20d common
8	0.162	WH 8-1, 16d common
9	0.148	WH 8-1, 10d common; IRC R606.6.4.1.2 and R703.8.4.1 (0.148 in), but R703.8.3.2 prints 0.144 in
10	0.135	WH 8-2, 16d box
10-1/4	0.131	WH, 8d common
10-1/2	0.128	WH, 10d box
11	0.120	IRC R905.3.6 and Table R602.3(1)
11-1/2	0.113	WH, 6d common, 8d box
12	0.105	IRC R905.2.5, asphalt shingle nails
12-1/2	0.099	WH, 6d and 7d box
14	0.080	WH 8-2, 4d and 5d box
14-1/2	0.076	WH, 3d box

An 8 gauge nail (the 16d common, 0.162 in) is 26% thicker than 8 AWG copper wire at 0.1285 in. The 12 gage roofing nail at 0.105 in and the law's 12 gauge sheet at 0.109 in happen to land close; at 16, sheet (0.0625 in) and AWG (0.0508 in) are 23% apart.

Why sheet gauge is a weight, not a thickness

The 1893 act defines each gauge in ounces per square foot and calls its thicknesses approximate, because rolled sheet is sold and taxed by weight. Its thicknesses assume wrought iron at 40 lb per square foot per inch. Circular 391 explains that steel weighs 2% more, so the same weight of steel is 2% thinner, and that galvanized sheet gauge is a weight for the finished sheet with the zinc included.

So a 16 gauge sheet is first of all 2.5 lb per square foot. Whether that is 0.0625, 0.0613 or 0.0598 in depends on which density the chart uses, and the law also allows 2.5% either way.

Frequently asked questions

How thick is 16 gauge steel?: 0.0625 in (1/16 in) in the 1893 US Standard Gauge, 0.0613 in at steel density, and 0.0598 in on supplier charts using the Manufacturers Standard Gauge. Galvanized 16 gauge is 0.0635 in on those charts.
How thick is 14 gauge steel?: 0.078125 in (5/64 in) in the US Standard Gauge, 0.0766 in at steel density and 0.0747 in on supplier charts. 14 AWG aluminum is 0.0641 in.
How thick is 18 gauge steel?: 0.05 in (1/20 in) in the US Standard Gauge, 0.0490 in at steel density and 0.0478 in on supplier charts.
How thick is 20 gauge steel?: 0.0375 in (3/80 in) in the US Standard Gauge, 0.0368 in at steel density and 0.0359 in on supplier charts.
How thick is 22 gauge?: 0.03125 in (1/32 in) in the US Standard Gauge and 0.0299 in on supplier charts. IRC Table R703.8.4(1) uses 0.0299 in and calls it 22 U.S. gage.
How thick is 26 gauge metal?: 0.01875 in in the US Standard Gauge and 0.0179 in on supplier charts. The IRC writes No. 26 as 0.019 in for flashing (R903.2.1) and 0.0187 in elsewhere (R1005.8).
Is a higher gauge thicker or thinner?: Thinner. In every gauge on this page a larger number is a thinner sheet or wire: 10 gauge steel is 0.1406 in in the US Standard Gauge and 20 gauge is 0.0375 in.
What gauge is 1/8 inch?: 11 gauge in the US Standard Gauge is exactly 1/8 in (0.125 in). On supplier charts 11 gauge is 0.1196 in, and 8 AWG aluminum is 0.1285 in.
How do I convert gauge to mm?: Multiply the inch thickness by 25.4. 16 gauge US Standard Gauge is 1.59 mm, 0.0598 in supplier gauge is 1.52 mm, and 16 AWG is 1.29 mm.

Check these numbers yourself

15 U.S.C. 206, Standard gauge for sheet and plate iron and steelUnited States Code, Title 15, Section 206 (Act of March 3, 1893, ch. 221, 27 Stat. 746), read through the Legal Information Institute. The full table, gauges 0000000 to 38. Read 2026-10-02.
Standard Thicknesses, Weights, and Tolerances of Sheet Metal, NBS Circular 391National Bureau of Standards, 1931, compiled by I. H. Fullmer and D. R. Miller. Table 1 (US Standard Gauge with the steel column at 40.80 lb per sq ft per inch), Table 7 (galvanized sheet gage) and Section III.1 (American wire gage for nonferrous sheet). Read 2026-10-02.
Copper Wire Tables, NBS Circular 31, 4th editionNational Bureau of Standards. The American wire gage law, No. 0000 = 0.4600 in to No. 36 = 0.0050 in by geometric progression. Read 2026-09-08.
Welders Supply, Metal Gauge to Thickness ChartWelders Supply, published June 17, 2026, updated June 23, 2026. Used only for the supplier convention: Manufacturers Standard Gauge, 41.82 lb per sq ft per inch, and its steel and galvanized values for 10, 16, 22, 24 and 26 gauge. Read 2026-10-02.
Utah Residential Code 2021, Chapters 3, 6, 7, 9, 10 and 13IRC 2021 as adopted in Utah, read through UpCodes: R302.5.2, R606.6.4.1.2, R703.8.3.2, R703.8.4.1, Table R703.8.4(1), R903.2.1, R905.7.6, R905.8.8, R1005.8, Table M1306.2, M1308.2.3 and Table M1601.1.1. Read 2026-10-02.
USDA Forest Products Laboratory, Wood Handbook, Chapter 8 Fastenings (FPL-GTR-282)Wood Handbook: Wood as an Engineering Material, General Technical Report FPL-GTR-282, USDA Forest Service, Forest Products Laboratory, 2021. Chapter 8, pages 8-2 to 8-13. A US government publication in the public domain. Read 2026-10-02.

How every figure here is verified: Sources & Method. Who builds this: Lucas Pradella, and the method is on About. Found something wrong? Tell us and it gets fixed or removed.

Figures on this page last checked against the source documents on 2026-10-02. Codes are amended locally; confirm against the edition your jurisdiction enforces.

Related calculators

Nominal figures. The law allows 2.5% either way and mills work to tolerances; where a code or drawing gives a minimum decimal thickness, that decimal governs, not the gauge number.