# Inches to Fraction Calculator

Convert decimal inches to fractions (e.g., 0.375 to 3/8). Choose precision from halves to 64ths. Shows rounding error and millimeters.

## What this calculates

Convert decimal inch measurements to fractions for woodworking, machining, and construction. Enter a decimal value and choose your precision, and the calculator gives you the closest standard fraction.

## Inputs

- **Decimal Inches** (in) — min 0 — Enter a decimal inch value (e.g., 0.375).
- **Fraction Precision** — options: Nearest 1/2, Nearest 1/4, Nearest 1/8, Nearest 1/16, Nearest 1/32, Nearest 1/64 — Choose how fine the fractional result should be. 1/16 and 1/32 are common in woodworking.

## Outputs

- **Fraction** — formatted as text — Decimal value expressed as a simplified fraction of an inch.
- **Whole + Fraction** — formatted as text — Whole inches plus fractional remainder (e.g., 2-3/8).
- **Millimeters** (mm) — Equivalent in millimeters (1 inch = 25.4 mm).
- **Rounding Error** (in) — Difference between the exact decimal and the rounded fraction.

## Details

Tape measures and drill bits are labeled in fractions of an inch, but digital calipers and CAD software output decimals. This calculator bridges the gap by converting any decimal inch value to the nearest standard fraction.

**How it works:** The calculator multiplies the decimal portion by your chosen denominator, rounds to the nearest whole number, and simplifies the resulting fraction.

**Common Decimal-to-Fraction Conversions:**

| Decimal | Fraction | mm |
|---------|----------|-----|
| 0.0625 | 1/16" | 1.588 |
| 0.125 | 1/8" | 3.175 |
| 0.1875 | 3/16" | 4.763 |
| 0.25 | 1/4" | 6.350 |
| 0.3125 | 5/16" | 7.938 |
| 0.375 | 3/8" | 9.525 |
| 0.4375 | 7/16" | 11.113 |
| 0.5 | 1/2" | 12.700 |
| 0.5625 | 9/16" | 14.288 |
| 0.625 | 5/8" | 15.875 |
| 0.6875 | 11/16" | 17.463 |
| 0.75 | 3/4" | 19.050 |
| 0.8125 | 13/16" | 20.638 |
| 0.875 | 7/8" | 22.225 |
| 0.9375 | 15/16" | 23.813 |

**Choosing precision:** For general woodworking, 1/16" is usually fine. Machining typically needs 1/32" or 1/64". The rounding error output shows how far off the fraction is from the exact decimal, so you can judge if the precision is good enough for your project.

## Frequently Asked Questions

**Q: How do I convert 0.375 inches to a fraction?**

A: 0.375 inches equals 3/8 inch. You can find this by multiplying 0.375 by 8 (the denominator), which gives 3. So the fraction is 3/8. In millimeters, that is 9.525 mm.

**Q: What fraction precision should I use for woodworking?**

A: Most woodworking projects use 1/16-inch precision. Fine joinery and machining may call for 1/32 or 1/64 inch. General construction typically rounds to the nearest 1/8 inch. Choose the precision that matches your tool markings and project tolerance.

**Q: How do I read fractions on a tape measure?**

A: The longest marks after each inch are 1/2", then 1/4" marks, then 1/8", then 1/16". Each successively shorter mark represents a finer fraction. Count the number of smallest marks from the last whole inch to determine the fraction.

**Q: Why does the calculator show a rounding error?**

A: Not every decimal converts to an exact standard fraction. For example, 0.333 inches is close to 1/3, but 1/3 is not a standard power-of-two fraction. The nearest 1/16 is 5/16 (0.3125), which has a rounding error of 0.0205 inches. The error tells you how accurate the fractional approximation is.

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Source: https://vastcalc.com/calculators/conversion/inches-to-fraction
Category: Conversion
Last updated: 2026-04-08