Formula: 1 inch = 25,4 mm
With this formula you can calculate all sizes. For your convenience, a table with the most common sizes is given below.
The bold sizes are also used for tool connections like for sockets and bits.
| Millimeters | Inches | |
| 1,27 | 1/20 | |
| 1,59 | 1/16 | (=4/64) |
| 1,98 | 5/64 | |
| 2,38 | 3/32 | (=6/64) |
| 2,78 | 7/64 | |
| 3,18 | 1/8 | (=8/64) |
| 3,57 | 9/64 | |
| 3,91 | 5/32 | (=10/64) |
| 4,76 | 3/16 | (=12/64) |
| 5,16 | 13/64 | |
| 5,56 | 7/32 | (=14/64) |
| 6,35 | 1/4 | (=16/64) |
| 7,14 | 9/32 | (=18/64) |
| 7,94 | 5/16 | (=20/64) |
| 8,73 | 11/32 | (=22/64) |
| 9,53 | 3/8 | (=24/64) |
| 10,32 | 13/32 | (=26/64) |
| 11,11 | 7/16 | (=28/64) |
| 12,70 | 1/2 | (=32/64) |
| 14,29 | 9/16 | (=36/64) |
| 15,88 | 5/8 | (=40/64) |
| 17,46 | 11/16 | (=44/64) |
| 19,05 | 3/4 | (=48/64) |
| 20,64 | 13/16 | (=52/64) |
| 22,23 | 7/8 | (=56/64) |
| 23,81 | 15/16 | (=60/64) |
| 25,40 | 1 | (=64/64) |
| 26,99 | 1.1/16 | (=68/64) |
| 28,58 | 1.1/8 | (=72/64) |
| 30,16 | 1.3/16 | (=76/64) |
| 31,75 | 1.1/4 | (=80/64) |
| 33,34 | 1.5/16 | (=84/64) |
| 34,93 | 1.3/8 | (=88/64) |
| 36,51 | 1.7/16 | (=92/64) |
| 38,10 | 1.1/2 | (=96/64) |
| 39,69 | 1.9/16 | (=100/64) |
| 41,28 | 1.5/8 | (=104/64) |
| 42,86 | 1.11/16 | (=108/64) |
| 44,45 | 1.3/4 | (=112/64) |
| 46,04 | 1.13/16 | (=116/64) |
| 47,63 | 1.7/8 | (=120/64) |
| 49,21 | 1.15/16 | (=124/64) |
| 50,80 | 2 | (=128/64) |
