Fraction calculator

Fractions appear in recipes, construction measurements, school maths and ratios. Working with them requires common denominators and simplification, which is easy to get wrong. This calculator performs the four basic operations on fractions and mixed numbers, simplifies the answer and converts it to a decimal.

How to use it

1. Enter the first fraction, for example 3/4 or a mixed number such as 1 1/2.
2. Choose the operation.
3. Enter the second fraction.
4. Read the simplified result, the mixed number form and the decimal.

How each operation works

• Add / subtract: rewrite with a common denominator. 1/3 + 1/4 = 4/12 + 3/12 = 7/12.
• Multiply: multiply tops and bottoms. 2/3 × 3/5 = 6/15 = 2/5.
• Divide: multiply by the reciprocal. 3/4 ÷ 1/8 = 3/4 × 8/1 = 6.
• Simplify: divide numerator and denominator by their greatest common divisor. 18/24 becomes 3/4 (GCD 6).

Worked example with mixed numbers

2 1/2 - 1 2/3: convert to improper fractions, 5/2 - 5/3 = 15/6 - 10/6 = 5/6, which is about 0.833.

Decimals to fractions

0.375 = 375/1000 = 3/8. Repeating decimals like 0.333... equal 1/3 exactly, but a calculator working with a finite number of digits can only approximate them.

Practical uses

• Scaling recipes, such as 3/4 cup × 1.5 = 1 1/8 cups.
• Imperial measurements, such as 5/16 inch + 3/8 inch = 11/16 inch.