Uses the exact factor 1 inch = 2.54 cm, fixed by international agreement in 1959. Screen sizes and tyre diameters are measured on the diagonal, so converting a stated size does not give you a width.
| cm | inches | inches | cm |
|---|---|---|---|
| 1 | 0.3937 | 1 | 2.54 |
| 5 | 1.9685 | 2 | 5.08 |
| 10 | 3.937 | 6 | 15.24 |
| 15 | 5.9055 | 12 | 30.48 |
| 30 | 11.811 | 24 | 60.96 |
| 100 | 39.3701 | 36 | 91.44 |
| 152 | 59.8425 | 60 | 152.4 |
| 180 | 70.8661 | 72 | 182.88 |