Last updated: November 18, 2025
Inches to fraction explained
Shop drawings and CNC programs often use decimal inches, while carpenters and machinists still prefer fractions like 5/32 or 1/64. This calculator normalizes any input (decimal inches or metric) into meters, converts to inches, then rounds to the nearest fraction using whatever denominator (up to 1/64) you specify.
How the conversion works
- Convert your entry to pure inches ( or decimal inches directly).
- Multiply the fractional portion by the chosen denominator (e.g., 64), round to the nearest whole number, and simplify the fraction.
The whole inches stay intact while the remainder becomes a numerator over the selected denominator.
Units and conversions
| Unit | Relation |
|---|---|
| Inch | (exact) |
| Fractional inch | numerator/denominator of an inch |
| Denominators | 2, 4, 8, 16, 32, 64 supported |
| Metric reference | cm/mm shown alongside results |
Worked examples
- Decimal to fraction
Convert 2.375 in to a 1/64-based fraction.
Result: 2 3/8 in.
- Metric to fractional inches
Translate 35 mm to a fractional inch (nearest 1/16).
Result: about 1 3/8 in (with metric reference 35 mm).
Tips and pitfalls
- Choose the smallest denominator that matches your tooling; cabinetry often stops at 1/16, precision machining may need 1/64.
- Decimal inches from CAD often include thousandths—round only after converting to avoid accumulating errors.
- When the rounded numerator equals the denominator (e.g., 7.999/8 rounds to 8/8), bump the whole-inch count by one and reset the fraction to 0.
- If you receive drawings in mm, convert everything to fractional inches before handing them to field crews to avoid mix-ups.