Where do these numbers come from?
- NISTSP 811 exact unit definitions (1 in = 25.4 mm, 1 lb = 453.59237 g)current edition
- NISTHandbook 44, weights and measurescurrent edition
- King Arthur BakingIngredient Weight Chart (kitchen tools)retrieved Oct 23, 2026
Checked Oct 23, 2026. 1 inch is exactly 25.4 mm (NIST SP 811), so 100 mm ÷ 25.4 = 3.937 in.
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12 mm = 0.4724 in
Worked example
12 ÷ 25.4 = 0.4724 inches. On a ruler marked in sixteenths, that is about 1/2″; in thirty-seconds, 15/32″; in sixty-fourths, 15/32″. The nearest 1/16 mark (1/2″ = 12.7 mm) is off by 0.7 mm.
12 mm is also 1.2 cm.
| Millimeters | Inches | Nearest 1/16 |
|---|---|---|
| 7 mm | 0.2756 | 1/4″ |
| 8 mm | 0.315 | 5/16″ |
| 9 mm | 0.3543 | 3/8″ |
| 10 mm | 0.3937 | 3/8″ |
| 11 mm | 0.4331 | 7/16″ |
| 12 mm | 0.4724 | 1/2″ |
| 13 mm | 0.5118 | 1/2″ |
| 14 mm | 0.5512 | 9/16″ |
| 15 mm | 0.5906 | 9/16″ |
| 16 mm | 0.6299 | 5/8″ |
| 17 mm | 0.6693 | 11/16″ |
Frequently asked questions
How many inches is 12 mm?
0.4724 inches, about 1/2″.
What fraction of an inch is 12 mm?
About 15/32″ to the nearest 1/32.