Inches to MM Converter
Inches into millimeters — decimals in, exact metric out.
Type in either field — the other updates instantly.
Inches to MM chart
| Inches | Millimeters |
|---|---|
| 0.0625 in | 1.59 mm |
| 0.125 in | 3.18 mm |
| 0.1875 in | 4.76 mm |
| 0.25 in | 6.35 mm |
| 0.375 in | 9.52 mm |
| 0.5 in | 12.7 mm |
| 0.625 in | 15.88 mm |
| 0.75 in | 19.05 mm |
| 1 in | 25.4 mm |
| 1.5 in | 38.1 mm |
| 2 in | 50.8 mm |
| 4 in | 101.6 mm |
| 12 in | 304.8 mm |
The rows are the workshop fractions: 1/16, 1/8, 3/16, 1/4, 3/8, 1/2, 5/8, 3/4.
How this is calculated
mm = inches × 25.4 (exact)
The drawing-to-metric direction: 0.375 in (3/8) is 9.525 mm, 0.5 in is 12.7 mm, a 1.75 in pipe is 44.45 mm. Enter fractions as decimals (1/16 = 0.0625, 1/8 = 0.125, 3/16 = 0.1875) and the ×25.4 multiply is exact every time.
Exact by definition — and conveniently reversible in your head: the common fractions land on clean metric numbers (1/2 in = 12.7 mm, 1/4 = 6.35, 1/8 = 3.175), a byproduct of the 25.4 definition.
Frequently asked questions
What is 3/8 inch in mm?
9.525 mm exactly (0.375 × 25.4). Rounded 9.5 mm is fine for woodwork; machinists keep the last digit.
How do I enter fractions?
As decimals: divide top by bottom. 5/16 = 0.3125 → 7.9375 mm. The chart above covers the standard set so most lookups need no division at all.
What is 1 inch in mm — exactly?
25.4 mm, exact by international definition since 1959. Not 25, not 25.5 — the difference is a broken fit in anything precision.
Are TV inches converted the same way?
Yes — a 65-inch screen has a 1,651 mm diagonal. Width and height then depend on the 16:9 shape: roughly 1,439 × 809 mm for that 65.