Calculator · Measuring & layout
Fraction to decimal converter (inches and mm)
Type a decimal, a fraction or millimeters. See it in decimal inches, to the nearest 1/16, 1/32 and 1/64 inch, and in millimeters.
Calculator
Examples: .625 · 5/8 · 1-3/16 · 1 3/16 · 25 mm
0.625 in = 15.875 mm
- Nearest 1/16
- 5/8 in
- Nearest 1/32
- 5/8 in
- Nearest 1/64
- 5/8 in
How the conversion works
- Fraction to decimal: divide the top number by the bottom number. 5 ÷ 8 = 0.625.
- Decimal to the nearest fraction: multiply by 16 (or 32, or 64), round to a whole number, then reduce. 0.625 × 16 = 10, so 10/16 = 5/8.
- Inches to millimeters: multiply by 25.4. One inch is exactly 25.4 mm.
Worked examples
| You type | Decimal inches | Nearest 1/16 | Nearest 1/64 | Millimeters |
|---|---|---|---|---|
| .625 | 0.625 | 5/8 | 5/8 | 15.875 |
| 1-3/16 | 1.1875 | 1 3/16 | 1 3/16 | 30.1625 |
| 25 mm | 0.984 | 1 | 63/64 | 25 |
The 1/16-inch chart
Every mark on a standard US tape between 0 and 1 inch.
| Fraction | Decimal inch | Millimeters |
|---|---|---|
| 1/16" | 0.0625 | 1.5875 |
| 1/8" | 0.125 | 3.175 |
| 3/16" | 0.1875 | 4.7625 |
| 1/4" | 0.25 | 6.35 |
| 5/16" | 0.3125 | 7.9375 |
| 3/8" | 0.375 | 9.525 |
| 7/16" | 0.4375 | 11.1125 |
| 1/2" | 0.5 | 12.7 |
| 9/16" | 0.5625 | 14.2875 |
| 5/8" | 0.625 | 15.875 |
| 11/16" | 0.6875 | 17.4625 |
| 3/4" | 0.75 | 19.05 |
| 13/16" | 0.8125 | 20.6375 |
| 7/8" | 0.875 | 22.225 |
| 15/16" | 0.9375 | 23.8125 |
| 1" | 1 | 25.4 |
Questions people ask
Is .625 the same as 5/8?
Yes. 5 ÷ 8 = 0.625, so .625 inch and 5/8 inch are the same length: 15.875 mm.
How do I turn a decimal into sixteenths?
Multiply by 16 and round to a whole number. 0.625 × 16 = 10, so 10/16, which reduces to 5/8.
How many millimeters are in an inch?
Exactly 25.4 mm. The inch has been defined that way since 1959.
Sources
Change log: Nov 6, 2026: Rebuilt to spec: sourced reference data, formulas and worked examples; no unverified people or test claims.