How fractions are combined
To add or subtract, the calculator puts both fractions over a common bottom number by cross-multiplying: a/b + c/d = (a × d + c × b) / (b × d). Subtraction works the same way with a minus sign.
To multiply, multiply the top numbers together and the bottom numbers together. To divide, flip the second fraction and multiply.
The answer is then simplified by dividing the top and bottom by their highest common factor. If the top is bigger than the bottom, the mixed number shows the whole part and the fraction left over.
Worked examples
1/2 + 1/3 = (1 × 3 + 1 × 2) / (2 × 3) = 5/6, which is 0.833333 as a decimal.
7/4 − 1/2 = (7 × 2 − 1 × 4) / 8 = 10/8, which simplifies to 5/4. As a mixed number that's 1 1/4, or 1.25.
3/4 ÷ 1/8 = 3/4 × 8/1 = 24/4, which simplifies to 6.
Inputs for the fraction calculator
First fraction: top number
The numerator of the first fraction. Whole numbers only; it can be negative.
First fraction: bottom number
The denominator of the first fraction. It must be a whole number of 1 or more.
Operation
Choose add, subtract, multiply or divide.
Second fraction: top number
The numerator of the second fraction. Whole numbers only; it can be negative. It can't be 0 when dividing.
Second fraction: bottom number
The denominator of the second fraction. It must be a whole number of 1 or more.
CALCULATOR QUESTIONS
Fraction calculator questions
How do I enter a whole number?
Put the whole number on top and 1 on the bottom. For example, 3 is 3/1.
How do I enter a mixed number like 2 1/2?
Turn it into an improper fraction first: multiply the whole number by the bottom number and add the top. 2 1/2 becomes 5/2.
Why can't I divide by a fraction with 0 on top?
A fraction with 0 on top is zero, and you can't divide by zero.
How do I enter a negative fraction?
Put the minus sign on the top number. For example, enter −3 on top and 4 on the bottom for −3/4.