Fraction to decimal calculator
Type a size in any of the three fields, as a fraction of an inch, a decimal inch or millimeters, and the other two follow. The answer is rounded to the nearest 1/8, 1/16, 1/32 or 1/64 with the error shown, and if a drill bit, plywood or board comes in that size it is linked.
Typed here; the other two follow.
For example 0.375.
For example 9.5 (a comma works too).
Nearest 1/16
3/4 in
0.75 in, exact
| Nearest | Fraction | Error |
|---|---|---|
| 1/8 | 3/4 in | exact |
| 1/16 (chosen) | 3/4 in | exact |
| 1/32 | 3/4 in | exact |
| 1/64 | 3/4 in | exact |
At this size
Why: 3/4 in = 0.75 in = 19.05 mm.
Why these numbers?
The situation
You entered 3/4 in.
From your input: the fraction field
What that means
A fraction is its top number divided by its bottom one: 3 ÷ 4 = 0.75 in.
Arithmetic: exact by definition
So
An inch is 25.4 mm exactly, so mm = inches × 25.4: 0.75 × 25.4 = 19.05 mm.
The number
To the nearest 1/16: 0.75 × 16 = 12, rounded to 12 (a half rounds up), so 3/4 in = 0.75 in. It lands exactly on the fraction.
Arithmetic: exact by definition
Sources
How the conversion works
A fraction is its top number divided by its bottom one, so 3/8 is 0.375 inch. An inch is 25.4 millimeters exactly, by the international agreement of 1959, so 0.375 inch is 9.525 mm. Going back, divide millimeters by 25.4: 10 mm is 0.3937 inch.
To find the nearest fraction, multiply the decimal by the step you measure in and round to a whole number. For 10 mm to the nearest 64th, 0.3937 × 64 = 25.197, which rounds to 25, so 25/64 inch, 0.0031 inch small. A half rounds up. The table shows all four steps, so you can see whether your tape's 16ths are close enough or the part needs a 64th.
The fraction field takes 3/8, 1-1/4 or 1 1/4, and a decimal too. It is a text field because a phone's number pad has no slash. Millimeters take a decimal point or a comma. Your last size is kept in the address and in this browser, so a link you share opens with the same numbers.
For a whole table, see the fraction to decimal chart or the printable fraction chart. Plywood is sold by names that are not its size, which the plywood thickness chart explains.