Imperial to Metric Conversion Chart

Convert fractional and whole inches to millimetres, based on the exact standard of 1 inch = 25.4 mm.

  • 1. Find your whole inches in the right-hand table.
  • 2. Find the fraction in the main table.
  • 3. Add the two millimetre values together.

Fractions of an inch → mm

Fraction Decimal mm
0 0″ 0.000
1/64 0.0156″ 0.397
1/32 0.0312″ 0.794
3/64 0.0469″ 1.191
1/16 0.0625″ 1.587
5/64 0.0781″ 1.984
3/32 0.0938″ 2.381
7/64 0.1094″ 2.778
1/8 0.125″ 3.175
9/64 0.1406″ 3.572
5/32 0.1562″ 3.969
11/64 0.1719″ 4.366
3/16 0.1875″ 4.762
13/64 0.2031″ 5.159
7/32 0.2188″ 5.556
15/64 0.2344″ 5.953
1/4 0.25″ 6.350
17/64 0.2656″ 6.747
9/32 0.2812″ 7.144
19/64 0.2969″ 7.541
5/16 0.3125″ 7.938
21/64 0.3281″ 8.334
11/32 0.3438″ 8.731
23/64 0.3594″ 9.128
3/8 0.375″ 9.525
25/64 0.3906″ 9.922
13/32 0.4062″ 10.319
27/64 0.4219″ 10.716
7/16 0.4375″ 11.112
29/64 0.4531″ 11.509
15/32 0.4688″ 11.906
31/64 0.4844″ 12.303
1/2 0.5″ 12.700
33/64 0.5156″ 13.097
17/32 0.5312″ 13.494
35/64 0.5469″ 13.891
9/16 0.5625″ 14.287
37/64 0.5781″ 14.684
19/32 0.5938″ 15.081
39/64 0.6094″ 15.478
5/8 0.625″ 15.875
41/64 0.6406″ 16.272
21/32 0.6562″ 16.669
43/64 0.6719″ 17.066
11/16 0.6875″ 17.462
45/64 0.7031″ 17.859
23/32 0.7188″ 18.256
47/64 0.7344″ 18.653
3/4 0.75″ 19.050
49/64 0.7656″ 19.447
25/32 0.7812″ 19.844
51/64 0.7969″ 20.241
13/16 0.8125″ 20.637
53/64 0.8281″ 21.034
27/32 0.8438″ 21.431
55/64 0.8594″ 21.828
7/8 0.875″ 22.225
57/64 0.8906″ 22.622
29/32 0.9062″ 23.019
59/64 0.9219″ 23.416
15/16 0.9375″ 23.812
61/64 0.9531″ 24.209
31/32 0.9688″ 24.606
63/64 0.9844″ 25.003

Whole inches → mm

Inches mm
1″ 25.4
2″ 50.8
3″ 76.2
4″ 101.6
5″ 127.0
6″ 152.4
7″ 177.8
8″ 203.2
9″ 228.6
10″ 254.0
11″ 279.4
12″ 304.8
Example: 5 3/16″ = 5″ (127.0 mm) + 3/16″ (4.763 mm) = 131.763 mm

1 inch = 25.4 mm exactly. Millimetre values rounded to three decimal places.