1 tommur er jafnt og 25,4 millimetrar:
1 ″ = 25,4 mm
Fjarlægðin d í millimetrum (mm) er jöfn fjarlægðinni d í tommum (″) sinnum 25,4:
d (mm) = d (″) × 25,4
Umreikna 20 tommur í millimetra:
d (mm) = 20 ″ × 25,4 = 508 mm
| Tommur (") | Millimetrar (mm) |
|---|---|
| 0,01 ″ | 0,254000 mm |
| 1/64 ″ | 0,396875 mm |
| 1/32 ″ | 0,793750 mm |
| 1/16 ″ | 1,587500 mm |
| 0,1 ″ | 2,540000 mm |
| 1/8 ″ | 3,175 mm |
| 1/4 ″ | 6,35 mm |
| 1/2 ″ | 12,7 mm |
| 1 ″ | 25,4 mm |
| 2 ″ | 50,8 mm |
| 3 ″ | 76,2 mm |
| 4 ″ | 101,6 mm |
| 5 ″ | 127,0 mm |
| 6 ″ | 152,4 mm |
| 7 ″ | 177,8 mm |
| 8 ″ | 203,2 mm |
| 9 ″ | 228,6 mm |
| 10 ″ | 254,0 mm |
| 20 ″ | 508,0 mm |
| 30 ″ | 762,0 mm |
| 40 ″ | 1016,0 mm |
| 50 ″ | 1270,0 mm |
| 60 ″ | 1524,0 mm |
| 70 ″ | 1778,0 mm |
| 80 ″ | 2032,0 mm |
| 90 ″ | 2286,0 mm |
| 100 ″ | 2540,0 mm |