Sheet metal thickness is denoted by gauge, sometimes spelled gage, which indicates a standard thickness before processing.  Click here for a Gauge to mm Conversion Chart.  Processing may include polishing, or the applying of protective plastics which will decrease or increase a sheet’s thickness respectively.  As the gauge number increases the material’s thickness decreases.  Below is our best attempt to capture all of the standard gauge thickness of different materials.  Be sure to check with your supplier when purchasing steel what your actual thickness is going to be, especially if you’re receiving polished or treated material.

Gauge #Standard Steel (Inches)Standard Steel (mm)Strip / Tubing (Inches)Non-Ferrous / Aluminum (Inches)Non-Ferrous / Aluminum (mm)Galvanized Steel (Inches)Galvanized Steel (mm)US Standard
0000000-------.5000
000000---.580014.732--.4688
00000--.500.516513.119--.4375
0000--.454.460011.684--.4063
000--.425.409610.404--.3750
00--.380.36489.266--.3438
0--.340.32498.252--.3125
1--.300.28937.348--.2813
2--.284.25766.543--.2656
3.23916.073.259.22945.827--.2500
4.22425.695.238.20435.189--.2344
5.20925.314.220.18194.620--.2188
6.19434.935.203.16204.115--.2031
7.17934.554.180.14433.665--.1875
8.16444.176.165.12853.264-4.270.1719
9.14953.797.148.11442.906.15323.891.1563
10.13453.416.134.10192.588.13823.510.1406
11.11963.038.120.09072.304.12333.132.1250
12.10462.657.109.08082.052.10842.753.1094
13.08972.278.095.07201.829.09342.372.0938
14.07471.897.083.06411.628.07851.994.0781
15.06731.709.072.05711.450.07101.803.0703
16.05981.519.065.05081.290.06351.613.0625
17.05381.367.058.04531.151.05751.461.0563
18.04781.214.049.04031.024.05161.311.0500
19.04181.062.042.0359.912.04561.158.0438
20.0359.912.035.0320.813.03961.006.0375
21.0329.836.032.0285.724.0366.930.0344
22.0299.759.028.0253.643.0306.853.0313
23.0269.683.025.0226.574.0276.777.0281
24.0239.607.022.0201.511.0247.701.0250
25.0209.531.020.0179.455.0217.627.0219
26.0179.455.018.0159.404.0202.551.0188
27.0164.417-.0142.361.0187.513.0172
28.0149.378-.0126.320.0172.475.0156
29.0135.343-.0113.287.0157.437.0141
30.0120.305-.0100.254.0142.399.0125
31.0105.267-.0089.226.0134.361.0109
32.0097.246-.0080.203-.340.0102
33.0090.229-.0071.180--.0094
34.0082.208-.0063.160--.0086
35.0075.191-.0056.140--.0078
36.0067.170-.0050.127--.0070
37-.163-.0045.114--.0066
38-.152-.004.102--.0063
39----.089--.0059
40----.079--.0055
41-------.0053
42-------.0051
43-------.0049
44-------.0047

Sheet Metal Tolerances

Because sheets are rolled to the desired thickness there is almost always some crowning of the rollers, resulting in a thinner sheet on the edges compared to the center.

Steel / Stainless SteelAluminum
Thickness36'' Wide Sheet48'' Wide SheetThickness36'' Wide Sheet48'' Wide Sheet
.170 - .030.0015.002.018 - .028.002.0025
.031 - .041.002.003.029 - .036.002.0025
.042 - .059.003.004.037 - .045.0025.003
.060 - .073.003.0045.046 - .068.003.004
.074 - .084.004.0055.069 - .076.003.004
.085 - .099.004.006.077 - .096.0035.004
.100 - .115.005.007.097 - .108.004.005
.116 - .131.005.0075.109 - .125.0045.005
.132 - .146.006.009.126 - .140.0045.005
.147 - .187.007.0105.141 - .172.006.008
.173 - .203.007.010
.204 - .249.009.011

Galvanized Coating Thicknesses

As you can see from our first chart the galvanized columns are thicker than the regular steel.  The process of galvanizing bonds a layer of zinc to the steel.  This layer’s thickness can be controlled and the different thicknesses are designated below.  The thicknesses are based off of how many ounces per square foot of the galvanizing material is added to the base steel.

 Triple SpotSingle Spot
DesignationBoth SidesOne SideBoth Sides
G2352.35.802.00
G2102.10.721.80
G1851.85.641.60
G1651.65.561.40
G1401.40.481.20
G1151.15.401.00
G90.90.32.80
G60 / A60.60.20.50
G40 / A40.40.12.30
G30 / A30.30.10.25
A25.25.08.20