Here are helpful charts for determining Material Thickness of steel and aluminum, plus gage sizes.
 
 
  
                      
                        
                          | 
							
                          Gauge No. | 
                          
							Thickness | 
                         
                        
                          | 
							fraction | 
                          inch | 
                          mm | 
                         
                        
                          | 
							6 | 
                          13/64 | 
                          .2031 | 
                          5.16 | 
                         
                        
                          | 
							7 | 
                          3/16 | 
                          .1875 | 
                          4.76 | 
                         
                        
                          | 
							8 | 
                          11/64 | 
                          .1719 | 
                          4.37 | 
                         
                        
                          | 
							9 | 
                          5/32 | 
                          .1563 | 
                          3.97 | 
                         
                        
                          | 
							10 | 
                          9/64 | 
                          .1406 | 
                          3.57 | 
                         
                        
                          | 
							11 | 
                          
							1/8 | 
                          .1250 | 
                          3.18 | 
                         
                        
                          | 
							12 | 
                          7/64 | 
                          .1094 | 
                          2.78 | 
                         
                        
                          | 
							13 | 
                          3/32 | 
                          .0938 | 
                          2.38 | 
                         
                        
                          | 
							14 | 
                          5/64 | 
                          .0781 | 
                          1.98 | 
                         
                        
                          | 
							15 | 
                          - | 
                          .0703 | 
                          1.79 | 
                         
                        
                          | 
							16 | 
                          1/16 | 
                          .0625 | 
                          1.59 | 
                         
                        
                          | 
							17 | 
                          - | 
                          .0563 | 
                          1.43 | 
                         
                        
                          | 
							18 | 
                          - | 
                          .0500 | 
                          1.27 | 
                         
                        
                          | 
							19 | 
                          - | 
                          .0438 | 
                          1.11 | 
                         
                        
                          | 
							20 | 
                          - | 
                          .0375 | 
                          .953 | 
                         
                      	
                          | 
							21 | 
                          - | 
                          .0344 | 
                          .873 | 
                         
						
                          | 
							22 | 
                          1/32 | 
                          .0313 | 
                          .794 | 
                         
						
                          | 
							23 | 
                          - | 
                          .0218 | 
                          .714 | 
                         
						
                          | 
							24 | 
                          - | 
                          .0250 | 
                          .635 | 
                         
						
                          | 
							25 | 
                          - | 
                          .0219 | 
                          .556 | 
                         
						
                          | 
							26 | 
                          - | 
                          .0188 | 
                          .478 | 
                         
						
                          | 
							27 | 
                          - | 
                          .0172 | 
                          .437 | 
                         
						
                          | 
							28 | 
                          1/64 | 
                          .0156 | 
                          .396 | 
                         
						
                          | 
							29 | 
                          - | 
                          .0141 | 
                          .358 | 
                         
						
                          | 
							30 | 
                          - | 
                          .0125 | 
                          .318 | 
                         
						
                          | 
							31 | 
                          - | 
                          .0109 | 
                          .277 | 
                         
						
                          | 
							32 | 
                          - | 
                          .0102 | 
                          .259 | 
                         
						
                          | 
							33 | 
                          - | 
                          .0094 | 
                          .239 | 
                         
						
                          | 
							34 | 
                          - | 
                          .0086 | 
                          .218 | 
                         
						
                          | 
							35 | 
                          - | 
                          .0078 | 
                          .198 | 
                         
                       
 
  
Non-ferrous(Aluminum)  
vs.  
Ferrous(Steel & Stainless) 
|   | 
ALUMINUM | 
STEEL | 
 
| Gauge | 
inch | 
mm | 
inch | 
mm | 
 
| 3 | 
.2294 | 
5.827 | 
.2391 | 
6.073 | 
 
| 4 | 
.2043 | 
5.189 | 
.2242 | 
5.695 | 
 
| 5 | 
.1819 | 
4.620 | 
.2092 | 
5.314 | 
 
| 6 | 
.1620 | 
4.115 | 
.1943 | 
4.935 | 
 
| 7 | 
.1443 | 
3.665 | 
.1793 | 
4.554 | 
 
| 8 | 
.1285 | 
3.264 | 
.1644 | 
4.176 | 
 
| 9 | 
.1144 | 
2.906 | 
.1495 | 
3.797 | 
 
| 10 | 
.1019 | 
2.588 | 
.1345 | 
3.416 | 
 
| 11 | 
.0907 | 
2.304 | 
.1196 | 
3.030 | 
 
| 12 | 
.0808 | 
2.052 | 
.1046 | 
2.657 | 
 
| 13 | 
.0720 | 
1.829 | 
.0897 | 
2.278 | 
 
| 14 | 
.0641 | 
1.628 | 
.0747 | 
1.897 | 
 
| 15 | 
.0571 | 
1.450 | 
.0673 | 
1.709 | 
 
| 16 | 
.0508 | 
1.290 | 
.0598 | 
1.519 | 
 
| 17 | 
.0453 | 
1.151 | 
.0538 | 
1.367 | 
 
| 18 | 
.0403 | 
1.024 | 
.0478 | 
1.214 | 
 
| 19 | 
.0359 | 
0.912 | 
.0418 | 
1.062 | 
 
| 20 | 
.0320 | 
0.813 | 
.0359 | 
0.912 | 
 
| 21 | 
.0285 | 
0.724 | 
.0329 | 
0.836 | 
 
| 22 | 
.0253 | 
0.643 | 
.0299 | 
0.759 | 
 
| 23 | 
.0226 | 
0.574 | 
.0269 | 
0.683 | 
 
| 24 | 
.0201 | 
0.511 | 
.0239 | 
0.607 | 
 
| 25 | 
.0179 | 
0.455 | 
.0209 | 
0.531 | 
 
| 26 | 
.0159 | 
0.404 | 
.0179 | 
0.455 | 
 
| 27 | 
.0142 | 
0.361 | 
.0164 | 
0.417 | 
 
| 28 | 
.0126 | 
0.320 | 
.0149 | 
0.378 | 
 
| 29 | 
.0113 | 
0.287 | 
.0135 | 
0.343 | 
 
| 30 | 
.0100 | 
0.254 | 
.0120 | 
0.305 | 
 
| 31 | 
.0089 | 
0.226 | 
.0105 | 
0.267 | 
 
| 32 | 
.0080 | 
0.203 | 
.0097 | 
0.246 | 
 
| 33 | 
.0071 | 
0.180 | 
.0090 | 
0.229 | 
 
| 34 | 
.0063 | 
0.160 | 
.0082 | 
0.208 | 
 
| 35 | 
.0056 | 
0.142 | 
.0075 | 
0.191 | 
 
 
 
  
Fraction-Decimal-Millimeter Conversions
| 
 FRACTION  | 
 DECIMAL  | 
 MILLIMETER  | 
 
| 
 1/64   | 
 .0156   | 
.3969  | 
 
| 
 1/32   | 
 .0313   | 
.7938  | 
 
| 
 3/64   | 
 .0469   | 
1.1906  | 
 
| 
 1/16   | 
 .0625   | 
1.5875  | 
 
| 
 5/64   | 
 .0781   | 
1.9844  | 
 
| 
 3/32   | 
 .0938   | 
2.3813  | 
 
| 
 7/64   | 
 .1094   | 
2.7781  | 
 
| 1/8 | 
.125 | 
3.1750 | 
 
| 
 9/64   | 
 .1406   | 
3.5719  | 
 
| 
 5/32   | 
 .1563   | 
3.9688  | 
 
| 
 11/64   | 
 .1719   | 
4.3656  | 
 
| 
 3/16   | 
 .1875   | 
4.7625  | 
 
| 
 13/64   | 
 .2031   | 
5.1594  | 
 
| 
 7/32   | 
 .2188   | 
5.5563  | 
 
| 
 15/64   | 
 .2344   | 
5.9531  | 
 
| 1/4 | 
.250 | 
6.3500 | 
 
| 
 17/64   | 
 .2656   | 
 6.7469   | 
 
| 
 9/32   | 
 .2813   | 
 7.1438   | 
 
| 
 19/64   | 
 .2969   | 
 7.5406   | 
 
| 
 5/16   | 
 .3125   | 
 7.9375   | 
 
| 
 21/64   | 
 .3281   | 
 8.3344   | 
 
| 
 11/32   | 
 .3438   | 
 8.7313   | 
 
| 
 23/64   | 
 .3594   | 
 9.1281   | 
 
| 3/8 | 
.375 | 
9.5250 | 
 
| 
 25/64   | 
 .3906   | 
 9.9219   | 
 
| 
 13/32   | 
 .4063   | 
 10.3188   | 
 
| 
 27/64   | 
 .4219   | 
 10.7156   | 
 
| 
 7/16   | 
 .4375   | 
 11.1125   | 
 
| 
 29/64   | 
 .4531   | 
 11.5094   | 
 
| 
 15/32   | 
 .4688   | 
 11.9063   | 
 
| 
 31/64   | 
 .4844   | 
 12.3031   | 
 
| 1/2 | 
.500 | 
12.7000 | 
 
| 
 33/64   | 
 .5156   | 
 13.0969   | 
 
| 
 17/32   | 
 .5313   | 
 13.4938   | 
 
| 
 35/64   | 
 .5499   | 
 13.8906   | 
 
| 
 9/16   | 
 .5625   | 
 14.2875   | 
 
| 
 37/64   | 
 .5781   | 
 14.6844   | 
 
| 
 19/32   | 
 .5938   | 
 15.0813   | 
 
| 
 39/64   | 
 .6094   | 
 15.4781   | 
 
| 5/8 | 
.625 | 
15.8750 | 
 
| 
 41/64   | 
 .6406   | 
 16.2719   | 
 
| 
 21/32   | 
 .6563   | 
 16.6688   | 
 
| 
 43/64   | 
 .6719   | 
 17.0656   | 
 
| 
 11/16   | 
 .6875   | 
 17.4625   | 
 
| 
 45/64   | 
 .7031   | 
 17.8594   | 
 
| 
 23/32   | 
 .7188   | 
 18.2563   | 
 
| 
 47/64   | 
 .7344   | 
 18.6531   | 
 
| 3/4 | 
.750 | 
19.0500 | 
 
| 
 49/64   | 
 .7656   | 
 19.4469   | 
 
| 
 25/32   | 
 .7813   | 
 19.8438   | 
 
| 
 51/64   | 
 .7969   | 
 20.2406   | 
 
| 
 13/16   | 
 .8125   | 
 20.6375   | 
 
| 
 53/64   | 
 .8281   | 
 21.0344   | 
 
| 
 27/32   | 
 .8438   | 
 21.4313   | 
 
| 
 55/64   | 
 .8594   | 
 21.8281   | 
 
| 7/8 | 
.875 | 
22.2250 | 
 
| 
 57/64   | 
 .8906   | 
 22.6219   | 
 
| 
 29/32   | 
 .9063   | 
 23.0188   | 
 
| 
 59/64   | 
 .9219   | 
 23.4156   | 
 
| 
 15/16   | 
 .9375   | 
 23.8125   | 
 
| 
 61/64   | 
 .9531   | 
 24.2094   | 
 
| 
 31/32   | 
 .9688   | 
 24.6063   | 
 
| 
 63/64   | 
 .9844   | 
 25.0031   | 
 
| 1 | 
1.00 | 
25.400 | 
 
 
 
  
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