To turn a fraction of an inch into a decimal, divide the top number by the bottom number: 5/16" = 5 ÷ 16 = 0.3125". For millimeters, multiply the decimal by 25.4 (an inch is exactly 25.4 mm): 0.3125 × 25.4 = 7.9375 mm.
The first table lists every 1/64" up to 1". The 1/16ths, the marks on most tape measures, are in bold. Its decimals and millimeters are exact, not rounded.
To go from a decimal back to a fraction, multiply the decimal by 16 and round to a whole number: that many sixteenths. 0.3" × 16 = 4.8, which rounds to 5, so 5/16". For eighths multiply by 8, for 32nds by 32. The second table does this for 0.05" to 1.00".
Fractions of an inch to decimals and millimeters
Fractions of an inch to decimals and millimeters| Fraction | Decimal inch | Millimeters |
|---|
| 1/64" | 0.015625 | 0.396875 |
|---|
| 1/32" | 0.03125 | 0.79375 |
|---|
| 3/64" | 0.046875 | 1.190625 |
|---|
| 1/16" | 0.0625 | 1.5875 |
|---|
| 5/64" | 0.078125 | 1.984375 |
|---|
| 3/32" | 0.09375 | 2.38125 |
|---|
| 7/64" | 0.109375 | 2.778125 |
|---|
| 1/8" | 0.125 | 3.175 |
|---|
| 9/64" | 0.140625 | 3.571875 |
|---|
| 5/32" | 0.15625 | 3.96875 |
|---|
| 11/64" | 0.171875 | 4.365625 |
|---|
| 3/16" | 0.1875 | 4.7625 |
|---|
| 13/64" | 0.203125 | 5.159375 |
|---|
| 7/32" | 0.21875 | 5.55625 |
|---|
| 15/64" | 0.234375 | 5.953125 |
|---|
| 1/4" | 0.25 | 6.35 |
|---|
| 17/64" | 0.265625 | 6.746875 |
|---|
| 9/32" | 0.28125 | 7.14375 |
|---|
| 19/64" | 0.296875 | 7.540625 |
|---|
| 5/16" | 0.3125 | 7.9375 |
|---|
| 21/64" | 0.328125 | 8.334375 |
|---|
| 11/32" | 0.34375 | 8.73125 |
|---|
| 23/64" | 0.359375 | 9.128125 |
|---|
| 3/8" | 0.375 | 9.525 |
|---|
| 25/64" | 0.390625 | 9.921875 |
|---|
| 13/32" | 0.40625 | 10.31875 |
|---|
| 27/64" | 0.421875 | 10.715625 |
|---|
| 7/16" | 0.4375 | 11.1125 |
|---|
| 29/64" | 0.453125 | 11.509375 |
|---|
| 15/32" | 0.46875 | 11.90625 |
|---|
| 31/64" | 0.484375 | 12.303125 |
|---|
| 1/2" | 0.5 | 12.7 |
|---|
| 33/64" | 0.515625 | 13.096875 |
|---|
| 17/32" | 0.53125 | 13.49375 |
|---|
| 35/64" | 0.546875 | 13.890625 |
|---|
| 9/16" | 0.5625 | 14.2875 |
|---|
| 37/64" | 0.578125 | 14.684375 |
|---|
| 19/32" | 0.59375 | 15.08125 |
|---|
| 39/64" | 0.609375 | 15.478125 |
|---|
| 5/8" | 0.625 | 15.875 |
|---|
| 41/64" | 0.640625 | 16.271875 |
|---|
| 21/32" | 0.65625 | 16.66875 |
|---|
| 43/64" | 0.671875 | 17.065625 |
|---|
| 11/16" | 0.6875 | 17.4625 |
|---|
| 45/64" | 0.703125 | 17.859375 |
|---|
| 23/32" | 0.71875 | 18.25625 |
|---|
| 47/64" | 0.734375 | 18.653125 |
|---|
| 3/4" | 0.75 | 19.05 |
|---|
| 49/64" | 0.765625 | 19.446875 |
|---|
| 25/32" | 0.78125 | 19.84375 |
|---|
| 51/64" | 0.796875 | 20.240625 |
|---|
| 13/16" | 0.8125 | 20.6375 |
|---|
| 53/64" | 0.828125 | 21.034375 |
|---|
| 27/32" | 0.84375 | 21.43125 |
|---|
| 55/64" | 0.859375 | 21.828125 |
|---|
| 7/8" | 0.875 | 22.225 |
|---|
| 57/64" | 0.890625 | 22.621875 |
|---|
| 29/32" | 0.90625 | 23.01875 |
|---|
| 59/64" | 0.921875 | 23.415625 |
|---|
| 15/16" | 0.9375 | 23.8125 |
|---|
| 61/64" | 0.953125 | 24.209375 |
|---|
| 31/32" | 0.96875 | 24.60625 |
|---|
| 63/64" | 0.984375 | 25.003125 |
|---|
| 1" | 1 | 25.4 |
|---|
Decimal inches to the nearest 1/8", 1/16" and 1/32"
Decimal inches to the nearest 1/8", 1/16" and 1/32"| Decimal inch | 1/8" | 1/16" | 1/32" |
|---|
| 0.05" | 0" | 1/16" | 1/16" |
|---|
| 0.10" | 1/8" | 1/8" | 3/32" |
|---|
| 0.15" | 1/8" | 1/8" | 5/32" |
|---|
| 0.20" | 1/4" | 3/16" | 3/16" |
|---|
| 0.25" | 1/4" | 1/4" | 1/4" |
|---|
| 0.30" | 1/4" | 5/16" | 5/16" |
|---|
| 0.35" | 3/8" | 3/8" | 11/32" |
|---|
| 0.40" | 3/8" | 3/8" | 13/32" |
|---|
| 0.45" | 1/2" | 7/16" | 7/16" |
|---|
| 0.50" | 1/2" | 1/2" | 1/2" |
|---|
| 0.55" | 1/2" | 9/16" | 9/16" |
|---|
| 0.60" | 5/8" | 5/8" | 19/32" |
|---|
| 0.65" | 5/8" | 5/8" | 21/32" |
|---|
| 0.70" | 3/4" | 11/16" | 11/16" |
|---|
| 0.75" | 3/4" | 3/4" | 3/4" |
|---|
| 0.80" | 3/4" | 13/16" | 13/16" |
|---|
| 0.85" | 7/8" | 7/8" | 27/32" |
|---|
| 0.90" | 7/8" | 7/8" | 29/32" |
|---|
| 0.95" | 1" | 15/16" | 15/16" |
|---|
| 1.00" | 1" | 1" | 1" |
|---|
Rounding and how to use the chart
Rounding to the nearest 1/16" is how a tape measure is read: the answer is never more than 1/32" (0.03125", about 0.8 mm) off. When a cut has to be closer, use 1/32" or 1/64", or work in millimeters.
In the TrueSquare Calc app for Android, the Feet-Inch Calculator does these conversions offline on the job: type 0.3125" or 7.9375 mm and it shows 5/16", along with decimal feet and meters.
Frequently asked questions
How do you convert a fraction of an inch to a decimal?
Divide the top number by the bottom number. 3/8" = 3 ÷ 8 = 0.375". For a mixed number keep the whole inches: 2 3/8" = 2.375".
What is 1/16 of an inch as a decimal and in millimeters?
1/16" = 0.0625", which is 1.5875 mm (about 1.6 mm). 1/8" = 0.125" = 3.175 mm, and 1/32" = 0.03125" = 0.79375 mm.
How do you convert a decimal to the nearest 1/16 inch?
Multiply the decimal part by 16 and round to a whole number. 0.3" × 16 = 4.8, rounds to 5, so 5/16". For 2.7", 0.7 × 16 = 11.2 rounds to 11, so 2 11/16". The result is never more than 1/32" off.
How many millimeters are in an inch?
Exactly 25.4 mm, by international agreement since 1959. So 1/2" = 12.7 mm, 3/4" = 19.05 mm and 1/64" = 0.396875 mm.
Estimates only. Check measurements, product labels and local building codes before you buy or build.