When I first started mailling and looking around for ring sizes a LOT of them were in inches....it did my poor mind in trying to work out a conversion. I found a table similar to this one to be extremely helpful, and still refer to mine when it's not a size I am used to.
Have you got a ring ID that isn’t listed, here is how you can convert it yourself.
You need to convert the fraction to a decimal. You can do this by dividing the top number (numerator) by the bottom number (denominator). For example: 3/16 = 0.1875.
Next you need to convert the decimal value to metric. To do this you will need to multiply the decimal by 25.4. To continue our example 0.1875 x 25.4 = 4.7625 which when you round it out becomes 4.76mmID..3/16”= 4.76mmID.Your ideal metric size for a weave needing 3/16” would be a 4.75mmID ring.
At Aussie Maille we list imperial sizes in both mm and fractional inches.
4THS
| Fractions | Decimals | Millimetres |
| 1/4 | 0.25 | 6.35 |
| 1/2 | 0.50 | 12.70 |
8THS
| Fractions | Decimals | Millimetres |
| 1/8 | 0.125 | 3.18 |
| 3/8 | 0.375 | 9.53 |
| 5/8 | 0.625 | 15.88 |
16THS
| Fractions | Decimals | Millimetres |
| 1/16 | 0.06250 | 1.59 |
| 3/16 | 0.18750 | 4.76 |
| 5/16 | 0.31250 | 7.94 |
| 7/16 | 0.43750 | 11.11 |
| 9/16 | 0.56250 | 14.29 |
32NDS
| Fractions | Decimals | Millimetres |
| 1/32 | 0.03125 | 0.79 |
| 3/32 | 0.09375 | 2.38 |
| 5/32 | 0.15625 | 3.97 |
| 7/32 | 0.21875 | 5.56 |
| 9/32 | 0.28125 | 7.14 |
| 11/32 | 0.34375 | 8.73 |
| 13/32 | 0.40625 | 10.32 |
| 15/32 | 0.46875 | 11.91 |
| 17/32 | 0.53125 | 13.49 |
64THS
| Fractions | Decimals | Millimetres |
| 1/64 | 0.015625 | 0.40 |
| 3/64 | 0.046875 | 1.19 |
| 5/64 | 0.078125 | 1.98 |
| 7/64 | 0.109375 | 2.78 |
| 9/64 | 0.140625 | 3.57 |
| 11/64 | 0.171875 | 4.37 |
| 13/64 | 0.203125 | 5.16 |
| 15/64 | 0.234375 | 5.95 |
| 17/64 | 0.265625 | 6.75 |
| 19/64 | 0.296875 | 7.54 |
| 21/64 | 0.328125 | 8.33 |
| 23/64 | 0.359375 | 9.13 |
| 25/64 | 0.390625 | 9.92 |
| 27/64 | 0.421875 | 10.72 |
| 29/64 | 0.453125 | 11.51 |
| 31/64 | 0.484375 | 12.30 |