Fraction inch calculator
The calculator above multiplies any two numbers. For inches, multiply a decimal by 16 to get sixteenths, or by 25.4 for millimetres. The full sixteenths chart is below.
12 × 12 = 144
Adding 12 to itself 12 times gives the same answer.
Decimal inch to fraction, in one step
- Type the decimal part into the first box.
- Type 16 into the second box.
- Round the answer to the nearest whole number. That is your count of sixteenths.
- Reduce it if it halves cleanly: 8/16 is 1/2, 12/16 is 3/4.
So 0.4375 x 16 = 7, which is 7/16. And 0.62 x 16 = 9.92, which rounds to 10, so 10/16, or 5/8.
The sixteenths chart
| Fraction | Inches | Millimetres |
|---|---|---|
| 1/16 | 0.0625 | 1.59 |
| 1/8 | 0.125 | 3.18 |
| 3/16 | 0.1875 | 4.76 |
| 1/4 | 0.25 | 6.35 |
| 5/16 | 0.3125 | 7.94 |
| 3/8 | 0.375 | 9.53 |
| 7/16 | 0.4375 | 11.11 |
| 1/2 | 0.5 | 12.70 |
| 9/16 | 0.5625 | 14.29 |
| 5/8 | 0.625 | 15.88 |
| 11/16 | 0.6875 | 17.46 |
| 3/4 | 0.75 | 19.05 |
| 13/16 | 0.8125 | 20.64 |
| 7/8 | 0.875 | 22.23 |
| 15/16 | 0.9375 | 23.81 |
| 1 | 1.0 | 25.40 |
One inch is 25.4 millimetres exactly, so any inch figure becomes millimetres by putting 25.4 in the second box.
Going the other way
To turn a fraction into a decimal, divide the top by the bottom. 11/16 is 11 divided by 16, which is 0.6875. The decimal to fraction calculator handles the round trip.
When the answer looks wrong
Check the denominator first. A tape measure is marked in halves, quarters, eighths and sixteenths. If your answer comes out in thirds or fifths, it is not a tape-measure fraction, and something upstream used a metric figure. Also watch the rounding: 0.66 is nearer 11/16 than 5/8, and on a long cut that difference adds up.
To add several fractional lengths together, use the fraction adding calculator. The 16 times table is the same arithmetic in the other direction, and the rest live on calculators.