Metric to SAE Wrench and Socket Size Calculator

Your details

The wrench or socket size in millimeters you want to convert to the nearest SAE size.
mm
When converting metric to SAE, how large a gap to allow before flagging that no standard SAE size is close enough to substitute safely.
Exact decimal (inches)
0.3937in

The exact inch equivalent of the entered mm value (mm / 25.4)

Nearest SAE size3/8"
Nearest SAE - decimal0.375in
Gap to nearest SAE-0.0187in
Gap to nearest SAE-0.475mm
Fit assessmentModerate gap (0.0187 in / 0.475 mm) - use with care, prefer correct metric size
0.3937 in
Small (1/4")<0.25Medium (1/2")0.25-0.5Large (3/4")0.5-0.75Extra large (1"+)0.75+

10 mm converts to 0.39370 in; nearest SAE is 3/8".

  • Exact conversion: 10 mm / 25.4 = 0.39370 inches.
  • The nearest SAE size (3/8") is 0.475 mm smaller than the metric size.
  • Always prefer the correct metric wrench on metric fasteners - an oversized SAE wrench can round off the fastener head.

Next stepIf no metric tool is available, the nearest SAE size shown here is your best substitute - but go slowly and watch for slipping.

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