# Inches to Fraction Calculator

URL: https://speedycalculator.com/calculators/conversion/inches-to-fraction/
Last updated: 2026-10-25

> The inches to fraction calculator turns a decimal measurement such as 2.3125 in into the nearest fraction of an inch, like 2 5/16″, at the precision of your tape measure or ruler, and shows the rounding error.

## Inputs

- Decimal measurement (in, cm, mm, ft)
- Precision

## Results

- Nearest fraction
- In feet and inches
- Rounding error
- Exact value in mm

## Formula

```
fraction = round(decimal × denominator) ÷ denominator
```

## Explanation

Digital calipers and CAD drawings give decimal inches, while tape measures are marked in halves, quarters, eighths, sixteenths and sometimes thirty-seconds. This converts between the two.

### How to use the Inches to Fraction Calculator

- **Decimal measurement**
- **Precision**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Your value is multiplied by the chosen denominator, rounded to the nearest whole number and divided back, then reduced to its simplest fraction.

### Decimal to fraction chart (1/16″)

FractionDecimal inchmm1/16″0.06251.5871/8″0.12503.1753/16″0.18754.7621/4″0.25006.3505/16″0.31257.9383/8″0.37509.5257/16″0.437511.1121/2″0.500012.7009/16″0.562514.2875/8″0.625015.87511/16″0.687517.4623/4″0.750019.05013/16″0.812520.6377/8″0.875022.22515/16″0.937523.812

### Inputs explained

FieldWhat to enterDecimal measurementUnits: in, cm, mm, ftPrecisionChoose one: 1/2″, 1/4″, 1/8″, 1/16″ …

### What each result means

- **Nearest fraction** = round([Decimal measurement] ÷ 0.0254 × [Precision]) ÷ [Precision]
- **In feet and inches** = round([Decimal measurement] ÷ 0.0254 × [Precision]) ÷ [Precision]
- **Rounding error** = (round([Decimal measurement] ÷ 0.0254 × [Precision]) ÷ [Precision] - [Decimal measurement] ÷ 0.0254) × 25.4
- **Exact value in mm** = [Decimal measurement] × 1000

## Worked example

Inputs — Decimal measurement: 2.3125 in; Precision: 1/16″.

Results — **Nearest fraction = 2 5/16**; In feet and inches = 0 ft 2 5/16 in; Rounding error = 0 mm; Exact value in mm = 58.738 mm.

## FAQ

**What is 0.375 inch as a fraction?**
3/8″.

**What is 0.6 inch to the nearest 1/16?**
5/8″ (0.625″).

**How do I convert mm to a fraction of an inch?**
Choose mm as the unit; the calculator converts to inches first.

**What formula does the Inches to Fraction Calculator use?**
fraction = round(decimal × denominator) ÷ denominator.


## Sources

- [NIST Special Publication 811 – Guide for the Use of the International System of Units](https://www.nist.gov/pml/special-publication-811)
- [NIST Handbook 44 Appendix C – General tables of units of measurement](https://www.nist.gov/pml/owm/nist-handbook-44-current-edition)