Imperial to Metric Conversion Chart

Greyed out rows indicate standard fastening sizes.

Decimal (Inches)

Fraction (Inches)

mm
0.016 1/64 0.397
0.031 1/32 0.794
0.046 3/64 1.190
0.062 1/16 1.587
0.078 5/64 2.000
0.093 3/32 2.381
0.109 7/64 2.778
0.125 1/8 3.175
0.140 9/64 3.571
0.156 5/32 3.968
0.171 11/64 4.365
0.187 3/16 4.762
0.203 13/64 5.159
0.218 7/32 5.556
0.234 15/64 5.593
0.250 1/4 6.350
0.265 17/64 6.746
0.281 9/32 7.143
0.296 19/64 7.540
0.312 5/16 7.937
0.328 21/64 8.334
0.343 11/32 8.731
0.359 23/64 9.128
0.375 3/8 9.525
0.390 25/64 9.921
0.406 13/32 10.318
0.421 27/64 10.715
0.437 7/16 11.112
0.453 29/64 11.509
0.469 15/32 11.908
0.484 31/64 12.303
0.500 1/2 12.700
0.515 33/64 13.097
0.531 17/32 13.494
0.546 35/64 13.891
0.562 9/16 14.288
0.578 37/64 14.684
0.593 19/32 15.081
0.609 39/64 15.478
0.625 5/8 15.875
0.640 41/64 16.272
0.656 21/32 16.669
0.671 43/64 17.066
0.687 11/16 17.462
0.703 45/64 17.859
0.718 23/32 18.256
0.734 47/64 18.653
0.750 3/4 19.050
0.765 49/64 19.447
0.781 25/32 19.844
0.796 51/64 20.241
0.812 13/16 20.638
0.828 53/64 21.034
0.843 27/32 21.431
0.859 55/64 21.828
0.875 7/8 22.225
0.890 57/64 22.622
0.906 29/32 23.019
0.921 59/64 23.416
0.937 15/16 23.812
0.953 61/64 24.209
0.968 31/32 24.606
0.984 63/64 25.003
1.000 1 25.40
1.250 1-1/4 31.75
1.375 1-3/8 34.93
1.500 1-1/2 38.10
1.750 1-3/4 44.45
2.000 2 50.80
2.250 2-1/4 57.15
2.500 2-1/2 63.50
2.750 2-3/4 69.85
2.000 3 76.20
3.250 3-1/4 82.55
3.500 3-1/2 88.90
4.000 4 101.6
4.500 4-1/2 114.3
4.750 4-3/4 120.7
5.000 5 127.0
5.500 5-1/2 139.7
6.000 6 152.4
6.500 6-1/2 165.1
7.000 7 177.8
7.500 7-1/2 190.5
8.000 8 203.2
9.000 9 228.6
10.000 10 254.0