How often have you been working on a job where you need two of the same size sockets?
Instead of reaching for an adjustable spanner or an open ended wrench, how about using the metric or SAE equivalent?
A large number of socket sets have both SAE and metric sockets in the same case. But did you know that a good number of sockets are close to being the same size. In fact, they are often such a close match that cheaper sets sometimes leave out the metric equivalent.
The chart below converts SAE (inch system) wrenches to standard metric sized wrenches. So now you can pop a metric socket on the head of a bolt, and use the SAE socket on the nut end. Post this chart on your workshop wall or tool box lid to help find a close wrench fit.
It’s important to understand that the matches shown below are not always exact matches. However, they are certainly close enough to be interchanged – unless you are using a torque wrench or a breaker bar. I also wouldn’t use an equivalent size if the bolt is tight, stuck or damaged in any way.
In most cases, it is best to use 6 point sockets – the 12 point versions will cause greater slippage and may damage your bolt or nut.
The following sizes are good fits (less than 1% difference):
SAE | Metric |
---|---|
5/32″ | 4mm |
5/16″ | 8mm |
7/16″ | 11mm |
15/32″ | 12mm |
19/32″ | 15mm |
5/8″ | 16mm |
3/4″ | 19mm |
25/32″ | 20mm |
7/8″ | 22mm |
29/32″ | 23mm |
15/16″ | 24mm |
1-1/16″ | 27mm |
1-3/16″ | 30mm |
1-1/4″ | 32mm |
1-5/16″ | 33mm |
1-3/8″ | 35mm |
1-1/2″ | 38mm |
1-5/8″ | 41mm |
1-3/4″ | 44mm |
The following sizes are sloppy fits, and extra care should be taken:
WARNING : The sockets with bigger positive differences may damage your fastener by rounding the head. The negative differences may mean the socket is too small for the fastener.
SAE | Metric | Difference |
---|---|---|
9/32″ | 7mm | +2.05% |
3/8″ | 10mm | -4.75% |
1/2″ | 13mm | -2.31% |
9/16″ | 14mm | +2.05% |
21/32″ | 17mm | +1.95% |
11/16″ | 17mm | +2.72% |
13/16″ | 21mm | -1.73% |
1″ | 25mm | +1.60% |
1-1/8″ | 29mm | -1.47% |
1-7/16″ | 37mm | -1.32% |
Converting SAE socket sizes to metric measurements is fairly easy if you have a calculator at hand, or are excellent at mental arithmetic.
Most if the time you will find socket sizes are written as a fraction of an inch (eg 5/8″) This is also called an SAE or imperial measurement.
The reason we use 25.4 is because there are 25.4 millimeters in an inch (This figure never changes).
For example, 5/8″ is converted to metric as follows:
5 divided by 8 and multiplied by 25.4
On a calculator : 5 ÷ 8 × 25.4 = 15.875
When we look at this example, you can see that 16mm and 5/8″ are not an exact match.
But when we round the result to 16mm, they are only 0.125 of a millimeter apart. When this is expressed as a percentage difference, the result is only 0.78 of a percent (a very small amount – less than 1%).
Larger sockets are written as 1-3/8″ or 1 3/8″
There is an extra step to convert sockets that are an inch or larger.
On a calculator, 1-3/8″ is calculated as:
3 ÷ 8 × 25.4 + 25.4 = 34.925 mm (Rounds up to 35mm)
Socket Size |
1/4″ Drive |
3/8″ Drive |
1/2″ Drive |
3/4″ Drive |
1″ Drive |
mm | inch dec | Alternate Socket |
Variation inch dec |
---|---|---|---|---|---|---|---|---|---|
3mm | Y | 3.000 | 0.118 | ||||||
3.2mm | Y | 3.200 | 0.126 | ||||||
3.5mm | Y | 3.500 | 0.138 | ||||||
5/32″ | Y | 3.969 | 0.156 | 4mm | -0.001 | ||||
4mm | Y | 4.000 | 0.157 | 5/32″ | 0.001 | ||||
4.5mm | Y | 4.500 | 0.177 | ||||||
3/16″ | Y | 4.763 | 0.188 | ||||||
5mm | Y | 5.000 | 0.197 | ||||||
5.5mm | Y | Y | 5.500 | 0.217 | |||||
7/32″ | Y | Y | 5.556 | 0.219 | |||||
6mm | Y | Y | 6.000 | 0.236 | |||||
1/4″ | Y | Y | 6.350 | 0.250 | |||||
7mm | Y | Y | 7.000 | 0.276 | |||||
9/32″ | Y | Y | 7.144 | 0.281 | |||||
5/16″ | Y | Y | 7.938 | 0.313 | 8mm | -0.002 | |||
8mm | Y | Y | Y | 8.000 | 0.315 | 5/16″ | 0.002 | ||
11/32″ | Y | Y | Y | 8.731 | 0.344 | ||||
9mm | Y | Y | Y | 9.000 | 0.354 | ||||
3/8″ | Y | Y | Y | 9.525 | 0.375 | ||||
10mm | Y | Y | Y | 10.000 | 0.394 | ||||
11mm | Y | Y | Y | 11.000 | 0.433 | 7/16″ | -0.004 | ||
7/16″ | Y | Y | Y | 11.113 | 0.438 | 11mm | 0.004 | ||
15/32″ | Y | Y | Y | 11.906 | 0.469 | 12mm | -0.004 | ||
12mm | Y | Y | Y | 12.000 | 0.472 | 15/32″ | 0.004 | ||
1/2″ | Y | Y | Y | 12.700 | 0.500 | ||||
13mm | Y | Y | Y | 13.000 | 0.512 | ||||
14mm | Y | Y | Y | 14.000 | 0.551 | ||||
9/16″ | Y | Y | Y | 14.288 | 0.563 | ||||
15mm | Y | Y | Y | 15.000 | 0.591 | 19/32″ | -0.003 | ||
19/32″ | Y | 15.081 | 0.594 | 15mm | 0.003 | ||||
5/8″ | Y | Y | 15.875 | 0.625 | 16mm | -0.005 | |||
16mm | Y | Y | 16.000 | 0.630 | 5/8″ | 0.005 | |||
21/32″ | Y | 16.669 | 0.656 | ||||||
17mm | Y | Y | 17.000 | 0.669 | |||||
11/16″ | Y | Y | 17.463 | 0.688 | |||||
18mm | Y | Y | 18.000 | 0.709 | |||||
19mm | Y | Y | Y | 19.000 | 0.748 | 3/4″ | -0.002 | ||
3/4″ | Y | Y | Y | 19.050 | 0.750 | 19mm | 0.002 | ||
25/32″ | Y | Y | 19.844 | 0.781 | 20mm | -0.006 | |||
20mm | Y | Y | Y | 20.000 | 0.787 | 25/32″ | 0.006 | ||
13/16″ | Y | Y | Y | 20.638 | 0.813 | ||||
21mm | Y | Y | Y | 21.000 | 0.827 | ||||
22mm | Y | Y | Y | 22.000 | 0.866 | 7/8″ | -0.009 | ||
7/8″ | Y | Y | 22.225 | 0.875 | 22mm | 0.009 | |||
23mm | Y | Y | 23.000 | 0.906 | 29/32″ | -0.001 | |||
29/32″ | Y | Y | 23.019 | 0.906 | 23mm | 0.001 | |||
15/16″ | Y | Y | 23.813 | 0.938 | 24mm | -0.007 | |||
24mm | Y | Y | 24.000 | 0.945 | 15/16″ | 0.007 | |||
25mm | Y | Y | 25.000 | 0.984 | |||||
1″ | Y | 25.400 | 1.000 | ||||||
26mm | Y | Y | 26.000 | 1.024 | |||||
1-1/16″ | Y | Y | 26.988 | 1.063 | 27mm | 0.000 | |||
27mm | Y | Y | 27.000 | 1.063 | 1-1/16″ | 0.000 | |||
28mm | Y | Y | 28.000 | 1.102 | |||||
1-1/8″ | Y | Y | 28.575 | 1.125 | |||||
29mm | Y | Y | 29.000 | 1.142 | |||||
30mm | Y | Y | 30.000 | 1.181 | 1-3/16″ | -0.006 | |||
1-3/16″ | Y | Y | 30.163 | 1.188 | 30mm | 0.006 | |||
31mm | Y | 31.000 | 1.220 | ||||||
1-1/4″ | Y | Y | 31.750 | 1.250 | 32mm | -0.010 | |||
32mm | Y | 32.000 | 1.260 | 1-1/4″ | 0.010 | ||||
33mm | Y | 33.000 | 1.299 | 1-5/16″ | -0.013 | ||||
1-5/16″ | Y | 33.338 | 1.313 | 33mm | 0.013 | ||||
34mm | Y | 34.000 | 1.339 | ||||||
1-3/8″ | Y | 34.925 | 1.375 | 35mm | -0.003 | ||||
35mm | Y | 35.000 | 1.378 | 1-3/8″ | 0.003 | ||||
36mm | Y | Y | 36.000 | 1.417 | |||||
1-7/16″ | Y | 36.513 | 1.438 | ||||||
38mm | Y | Y | 38.000 | 1.496 | 1-1/2″ | -0.004 | |||
1-1/2″ | Y | Y | 38.100 | 1.500 | 38mm | 0.004 | |||
41mm | Y | Y | 41.000 | 1.614 | 1-5/8″ | -0.011 | |||
1-5/8″ | Y | Y | 41.275 | 1.625 | 41mm | 0.011 | |||
42mm | Y | 42.000 | 1.654 | ||||||
1-11/16″ | Y | Y | 42.863 | 1.688 | |||||
44mm | Y | 44.000 | 1.732 | 1-3/4″ | -0.018 | ||||
1-3/4″ | Y | Y | 44.450 | 1.750 | 44mm | 0.018 | |||
46mm | Y | 46.000 | 1.811 | 1-13/16″ | -0.001 | ||||
1-13/16″ | Y | Y | 46.038 | 1.813 | 46mm | 0.001 | |||
1-7/8″ | Y | Y | 47.625 | 1.875 | |||||
50mm | Y | 50.000 | 1.969 | ||||||
2″ | Y | Y | 50.800 | 2.000 | 2-1/8″ | -0.125 | |||
2-1/8″ | Y | Y | 53.975 | 2.125 | 54mm | 0.125 | |||
54mm | Y | 54.000 | 2.126 | ||||||
55mm | Y | 55.000 | 2.165 | ||||||
2-3/16″ | Y | Y | 55.563 | 2.188 | |||||
2-1/4″ | Y | Y | 57.150 | 2.250 | |||||
58mm | Y | 58.000 | 2.283 | ||||||
60mm | Y | 60.000 | 2.362 | 2-3/8″ | -0.013 | ||||
2-3/8″ | Y | 60.325 | 2.375 | 60mm | 0.013 | ||||
63mm | Y | 63.000 | 2.480 | ||||||
2-1/2″ | Y | 63.500 | 2.500 | ||||||
65mm | Y | 65.000 | 2.559 | ||||||
2-5/8″ | Y | 66.675 | 2.625 | ||||||
67mm | Y | 67.000 | 2.638 | ||||||
2-3/4″ | Y | 69.850 | 2.750 | ||||||
70mm | Y | 70.000 | 2.756 | ||||||
71mm | Y | 71.000 | 2.795 | ||||||
2-15/16″ | Y | 74.613 | 2.938 | ||||||
75mm | Y | 75.000 | 2.953 | ||||||
3″ | Y | 76.200 | 3.000 | ||||||
77mm | Y | 77.000 | 3.031 | ||||||
3-1/8″ | Y | 79.375 | 3.125 | ||||||
80mm | Y | 80.000 | 3.150 |