Imperial and Metric Spanner Sizes

The following chart shows the AF spanner sizes that should be used with UNC and UNF thread imperial bolts, along with the metric equivalent spanner size.

BOLT DIAMETER (INCHES) AF SPANNER SIZE (INCHES) SPANNER SIZE (MM)
  1/4 INCH 6.35 MM
  5/16 INCH 7.94 MM
  3/8 INCH 9.52 MM
1/4 INCH 7/16 INCH 11.11 MM
5/16 INCH 1/2 INCH 12.7 MM
3/8 INCH 9/16 INCH 14.29 MM
7/16 INCH 5/8 INCH 15.88 MM
  11/16 INCH 17.46 MM
1/2 INCH 3/4 INCH 19.05 MM
9/16 INCH 7/8 INCH 22.22 MM
5/8 INCH 15/16 INCH 23.81 MM
  1 INCH 25.40 MM
  1.1/16 INCH 26.93 MM
3/4 INCH 1.1/8 INCH 28.57 MM