Enter two fractions and choose add, subtract, multiply or divide. The answer is given in its simplest form, as a mixed number, as a decimal and as a percentage.
Results are estimates for planning. Check the figures before you make a financial or health decision.
How the Fraction calculator works
Enter the top (numerator) and bottom (denominator) of each fraction, then pick an operation.
- Add or subtract: the fractions are put over a common denominator. a/b + c/d = (a×d + c×b) ÷ (b×d).
- Multiply: multiply the tops and multiply the bottoms. a/b × c/d = (a×c) ÷ (b×d).
- Divide: flip the second fraction and multiply. a/b ÷ c/d = (a×d) ÷ (b×c).
The result is then simplified by dividing the top and bottom by their greatest common divisor. A negative sign is moved to the top.
The results show the simplified fraction, the mixed number (for example 1 5/12), the decimal to eight places and the percentage. Only whole numbers are accepted for the tops and bottoms, and a denominator of zero is rejected. Dividing by a fraction whose top is zero shows an error, since you cannot divide by zero.
Worked example
Using the default values in the calculator above:
| Input | Value |
|---|---|
| First fraction: top | 3 |
| First fraction: bottom | 4 |
| Operation | Add (+) |
| Second fraction: top | 2 |
| Second fraction: bottom | 3 |
Answer: 17/12
| Mixed number | 1 5/12 |
|---|---|
| Decimal | 1.41666667 |
| Percentage | 141.6667% |
Tips and common mistakes
If your fractions are mixed numbers, convert them first: 2 1/3 becomes (2×3 + 1)/3 = 7/3. Enter negatives in the numerator.
Check your answer by estimating. Adding two fractions that are each close to a half should give about one. If you need a decimal fraction or percentage, the extra rows give them directly. For comparing quantities, the Ratio calculator calculator may suit better, and Percentage of a number helps with percentages.
Frequently asked questions
How do I add fractions with different denominators?
Convert both to a common denominator, add the tops, and simplify. The calculator does this and shows the answer in its simplest form.
Can it handle mixed numbers?
Not directly. Convert a mixed number to an improper fraction first, for example 2 1/3 becomes 7/3, then enter it.
Why does it show an error when dividing?
You cannot divide by zero. If the second fraction’s top is 0, dividing by it is not possible.