How to calculate with fractions
- Type the First fraction: a fraction like 3/4, a mixed number like 1 2/3 (whole number, space, fraction) or a decimal.
- Pick the Operation and type the Second fraction.
- Read the answer in lowest terms, with the mixed number, decimal and percentage below it. The steps underneath show the working: the common denominator, the sum or product, and how it was simplified.
Rules for each operation
| Operation | Method | Example |
|---|---|---|
| Add | Common denominator, add the tops | 1/3 + 1/6 = 2/6 + 1/6 = 1/2 |
| Subtract | Common denominator, subtract the tops | 5/6 − 1/4 = 10/12 − 3/12 = 7/12 |
| Multiply | Tops times tops, bottoms times bottoms | 2/3 × 9/10 = 18/30 = 3/5 |
| Divide | Flip the second fraction, then multiply | 3/4 ÷ 1/2 = 3/4 × 2 = 3/2 |
With mixed numbers, turn them into improper fractions first: multiply the whole number by the denominator and add the top, so 1 2/3 becomes (1 × 3 + 2)/3 = 5/3. The calculator does this for you and shows the converted fractions in the result heading.
Reading the answer
The answer is always in lowest terms: the top and bottom are divided by their greatest common factor, so 18/30 becomes 3/5. An improper fraction such as 29/12 is also shown as a mixed number, 2 5/12, which is easier to picture when measuring or cooking.
The decimal is rounded to 10 places, so 29/12 shows as 2.4166666667. The percentage is handy for comparisons: 7/12 is about 58.33%, which tells you at a glance that it’s a bit more than half.