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Galvanized Steel Gauge Chart

Gauge (Ga.) is a measurement unit of the thickness of a thin material (such as sheet metal or plastic film). We often use gauges with numbers to show the thickness or diameter of materials. But the non-ferrous metal and mild steel of the same Ga., their thicknesses are different. Besides, steel sheets and pipes of the same Ga. are also different.

Generally, for the same material, the higher the number, the thinner the metal sheet. For example, 16 gauge galvanized steel sheet thickness is 1.6129 mm (0.0635 inches); while 18 gauge galvanized steel sheet thickness is 1.3106 mm (0.0516 inches).

Galvanized Steel Gauge Chart

The chart below shows the equivalent sheet gauge thickness in inches or millimeters.

Gauge (Ga.) Mild steel (Inch) Galvanized Steel (Inch) Aluminum (Inch) Mild steel (mm) Galvanized Steel (mm) Aluminum (mm)
3 0.2391 0.2294 6.0731 5.8268
4 0.2242 0.2043 5.6947 5.1892
5 0.2092 0.1819 5.3137 4.6203
6 0.1943 0.162 4.9352 4.1148
7 0.1793 0.1443 4.5542 3.6652
8 0.1644 0.1681 0.1285 4.1758 4.27 3.2639
9 0.1495 0.1532 0.1144 3.7973 3.8913 2.9058
10 0.1345 0.1382 0.1019 3.4163 3.5103 2.5883
11 0.1196 0.1233 0.0907 3.0378 3.1318 2.3038
12 0.1046 0.1084 0.0808 2.6568 2.7534 2.0523
13 0.0897 0.0934 0.072 2.2784 2.3724 1.8288
14 0.0747 0.0785 0.0641 1.8974 1.9939 1.6281
15 0.0673 0.071 0.0571 1.7094 1.8034 1.4503
16 0.0598 0.0635 0.0508 1.5189 1.6129 1.2903
17 0.0538 0.0575 0.0453 1.3665 1.4605 1.1506
18 0.0478 0.0516 0.0403 1.2141 1.3106 1.0236
19 0.0418 0.0456 0.0359 1.0617 1.1582 0.9119
20 0.0359 0.0396 0.032 0.9119 1.0058 0.8128
21 0.0329 0.0366 0.0285 0.8357 0.9296 0.7239
22 0.0299 0.0336 0.0253 0.7392 0.8531 0.6426
23 0.0269 0.0306 0.0226 0.6833 0.7772 0.574
24 0.0239 0.0276 0.0201 0.6071 0.7004 0.5105
25 0.0209 0.0247 0.0179 0.5309 0.6274 0.4547
26 0.0179 0.0217 0.0159 0.4547 0.5512 0.4039
27 0.0164 0.0202 0.0142 0.4166 0.5131 0.3607
28 0.0149 0.0187 0.0126 0.3785 0.475 0.32
29 0.035 0.0172 0.0113 0.3429 0.4369 0.287
30 0.012 0.0157 0.01 0.3048 0.3988 0.254
31 0.0105 0.0142 0.0089 0.2667 0.3607 0.2261
32 0.0097 0.0134 0.008 0.2464 0.3404 0.2032
33 0.009 0.0071 0.2286 0.1803
34 0.0082 0.0063 0.2083 0.16
35 0.0075 0.0056 0.1905 0.1422
36 0.0067 0.1702

How to Calculate the Weight of Galvanized Sheet?

Let’s take 28 gauge galvanized sheet metal 4×8 for example. The weight of galvanized sheet is calculated by the formula:

W= Thickness (mm) * Width (m) * Length (m) * 7.85 (Density of steel = 7.85 kg/m3) + zinc layer weight

28 gauge is 0.475 mm, and the width and length are about 1.219 m and 2.438 m. Then the weight is about 11 kg (0.475*1.219*2.438*7.85).

Which Is Thicker, 20 Gauge or 22 Gauge Steel?

For the same material, 20 gauge is thicker than 22 gauge. 2o gauge galvanized sheet is 1.0058 mm (0.0396”) in thickness, while 22 gauge is 0.8531 mm (0.0336”).

How About G90 Coating?

G90 indicates the zinc coating thickness of galvanized steel according to ASTM standards, such as G60, G140, etc. These numbers refer to the weight of zinc in Inch-Pound units of measurement. For example, G90 means the zinc coating of one square foot of sheet weighs 0.90 ounces.

1 oz/ft2 = 305.15 g/m2

So G90 (0.90 oz/ft2) = Z275 (275 g/m2)

Below is a table showing the commonly used codes for your reference.

ASTM A653 ISO Standard Zinc Weight
G40 Z120 120 g/m2
G60 Z180 180 g/m2
G90 Z275 275 g/m2
G115 Z350 350 g/m2

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