Inch Fraction Calculator
The tape measure speaks fractions — 3/8, 7/16, 1-3/4 — while plans, 3D printers and product pages speak decimals and millimeters. This calculator translates both ways: type a fraction and get the decimal and millimeter value, or type a decimal and get the nearest fraction to the 1/16th of an inch.
It also knows mixed fractions: 1-3/4 inches is one entry, not two fields. Everything updates as you type, so you can check 'is 14 mm closer to 9/16 or 5/8?' without leaving the page.
| Fraction | Decimal | MM |
|---|---|---|
| 1/8 | 0.125 | 3.175 |
| 1/4 | 0.25 | 6.35 |
| 3/8 | 0.375 | 9.525 |
| 1/2 | 0.5 | 12.7 |
| 5/8 | 0.625 | 15.875 |
| 3/4 | 0.75 | 19.05 |
| 7/8 | 0.875 | 22.225 |
| 1 | 1.0 | 25.4 |
How to use
- Type a fraction like 3/8 or a mixed one like 1-3/4 — decimal inches and millimeters appear instantly.
- Type a decimal like 0.375 to get the nearest fraction to the 1/16th of an inch.
- Check the nearest-16th table below for the tape-measure reading you need.
Frequently asked questions
What is 3/8 of an inch in decimals and mm?
3/8 inch = 0.375 inches = 9.525 mm. Type it into the converter to confirm, and check neighboring fractions (11/32 = 0.344, 13/32 = 0.406) when a measurement sits between marks.
How do I read fractions on a tape measure?
Between each inch mark, a tape divides into 16ths: the longest halfway mark is 1/2, quarter marks are 1/4 and 3/4, eighths next, and the shortest lines are 1/16 steps. Count lines from the inch mark and read top-down.
What is 0.375 inches as a fraction?
0.375 = 3/8 exactly. Multiply the decimal by 16: 0.375 × 16 = 6, so it is 6/16, which simplifies to 3/8. The calculator does this rounding automatically.
Why do my digital calipers disagree with the tape?
Calipers show decimal inches (or mm) to three places; tapes show fractions to the nearest 1/16 (0.0625). A tape reading of 9/16 (0.5625) and a caliper reading of 0.567 are the same measurement, rounded differently.