Fraction to Percent Calculator (Decimals Too)
Fraction, Decimal & Percent Converter
Fractions, decimals, and percentages are three ways of writing the same value: 3/8, 0.375, and 37.5% are identical. This converter moves between all three forms instantly — enter any one and get the others, with the fraction automatically reduced to its simplest terms.
The three conversions
- Fraction → percent: divide the numerator by the denominator, multiply by 100. 3/8 → 0.375 → 37.5%
- Decimal → percent: multiply by 100. 0.42 → 42%
- Percent → fraction: write it over 100 and simplify. 12.5% → 125/1000 → 1/8
Fraction, decimal & percent reference table
| Fraction | Decimal | Percent |
|---|---|---|
| 1/2 | 0.5 | 50% |
| 1/3 | 0.333… | 33.33% |
| 1/4 | 0.25 | 25% |
| 3/4 | 0.75 | 75% |
| 1/5 | 0.2 | 20% |
| 1/8 | 0.125 | 12.5% |
| 3/8 | 0.375 | 37.5% |
| 1/10 | 0.1 | 10% |
Ratios, ppm, and other conversions
A ratio converts the same way as a fraction: write it as a fraction and use the Fraction → Percent mode. A part-to-whole ratio like 3:5 means 3/5 = 60%. For a part-to-part ratio like 3:1, the first part is 3 of 4 total, so 3/4 = 75%.
Parts per million (ppm) is just a percentage on a different scale: 1% equals 10,000 ppm, so divide ppm by 10,000 to get a percent. 500 ppm = 500 ÷ 10,000 = 0.05%. The same logic converts ppm to a decimal (divide by 1,000,000).
Repeating decimals
Some fractions never terminate as decimals — 1/3 is 0.3333… forever, so as a percentage it's usually written 33.33% (or 33⅓%). The calculator rounds these for display while computing with full floating-point precision. To find a percentage of a number rather than convert its form, use the percentage calculator.
FAQs
Divide the numerator by the denominator, then multiply by 100. For 3/8: 3 ÷ 8 = 0.375, and 0.375 × 100 = 37.5%.
Multiply the decimal by 100 and add the % sign. 0.42 becomes 42%, and 1.5 becomes 150%.
Write the percentage over 100 and simplify. 12.5% = 12.5/100 = 125/1000, which reduces to 1/8. The calculator does the simplification for you.
1 ÷ 3 = 0.3333…, so 1/3 ≈ 33.33%. Some fractions produce repeating decimals; the calculator rounds them for display.
Yes. Any fraction whose numerator is larger than its denominator (an improper fraction) exceeds 100% — for example 5/4 = 125%.
Write the ratio as a fraction and convert. A part-to-whole ratio of 3:5 is 3/5 = 60%. A part-to-part ratio of 3:1 means 3 out of 4 total, so 3/4 = 75%. Use the Fraction → Percent mode.
Divide the ppm value by 10,000, because 1% equals 10,000 parts per million. So 500 ppm = 500 ÷ 10,000 = 0.05%.