Math CentralQuandaries & Queries


Question from philip, a parent:

Hi, I would like to know how to convert inches to mm in my head, I use socket sets and want to know an easy way to work out what 3/16, 7/32 is in mm. Thanks Phil

Hi Phil,

The wrenches measured in millimeters are not exactly the same size as the wrenches measured in inches so the best you can do is an approximation. One conversion factor I carry around in my head is the 2.54 cm = 1 inch. There are 10 millimeters in a centimeter so 25.4 mm = 1 in. If you divide both sides by 32 you get

1/32 in = 25.4/32 = 0.79375 mm


1/32 in is about 0.8 mm.

This may be what you need.

7 × 8 = 56 and hence 7/32 in is approximately 5.6 mm

3/16 = 6/32 and 6 × 8 = 48 so 3/16 in is approximately 4.8 mm.

I hope this helps,
Harley Weston

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