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Fraction Calculator
Sign up to favourite this calculatorEnter two fractions and pick an operation. The answer comes back in lowest terms, with the working, the mixed number and the decimal beside it.
3/4 + 1/3
Working
3/4 + 1/3 = 9/12 + 4/12 = 13/12As a mixed number
1 1/12As a decimal
1.08(3)As a percentage
108.3333%Save to My calculations
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Assumptions and limits
- An estimate from the numbers you entered, for guidance only. It is not financial, tax or medical advice.
- Calculator version 1, last updated 25 October 2026.
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How to use this calculator
- Type the first fraction as
3/4. A mixed number like2 3/4, a whole number like5and a decimal like0.75are all accepted. - Choose the operation: add, subtract, multiply or divide.
- Type the second fraction the same way.
- Read the answer in lowest terms, and check the working line for the intermediate step — the common denominator for a sum, or the flipped fraction for a division.
The three figures beside the answer are the same number in the forms people usually need next: as a mixed number, as a decimal, and as a percentage. A repeating decimal is shown with the repeating block in brackets, so 1/3 reads 0.(3) rather than a row of threes that has to stop somewhere.
What do I enter to calculate with fractions?
- First fraction and Second fraction — a fraction such as
3/4, a mixed number such as2 3/4, a whole number or a decimal. They start as 3/4 and 1/3. - Operation — add (+), subtract (−), multiply (×) or divide (÷).
- Limits — a denominator cannot be zero, and numerators and denominators must stay within 100,000,000 so the answer remains exact. Entries outside this are rejected with a message.
What do the results show?
- Answer — the exact result in lowest terms, headed by the sum you entered.
- Working — the middle step: the common denominator for a sum or difference, the multiplication across for a product, or the flipped second fraction for a division.
- As a mixed number — a whole part plus a fraction, or N/A (Proper fraction) when the result is below one.
- As a decimal and as a percentage — the same value, with repeating decimal digits in brackets.
- Common denominator — the lowest common multiple of the two denominators, shown for addition and subtraction.
How to calculate with fractions
Multiplying is the easy one: multiply straight across. Adding and subtracting need the two fractions to be counting the same thing first, which is what a common denominator does.
a/b + c/d = (a × d + c × b) / (b × d)
- a/b — the first fraction, e.g. 3/4
- c/d — the second fraction, e.g. 1/3
- b × d — a denominator both fractions divide into, e.g. 12
Multiplying the denominators always gives a common denominator, though not always the lowest one. The calculator uses the lowest common multiple, so 1/4 + 1/6 goes over 12 rather than 24 and the answer needs less reducing at the end.
Division is multiplication by the reciprocal — the second fraction turned upside down. That is why 1/2 ÷ 3/5 and 1/2 × 5/3 give the same 5/6.
Worked examples
| Sum | Middle step | Answer |
|---|---|---|
| 3/5 + 1/5 | same denominator, add the tops | 4/5 |
| 3/4 + 1/3 | 9/12 + 4/12 | 13/12 = 1 1/12 |
| 2/3 × 5/6 | (2 × 5) / (3 × 6) | 10/18 = 5/9 |
| 1/2 ÷ 3/5 | 1/2 × 5/3 | 5/6 |
| 2 3/4 − 1/2 | 11/4 − 2/4 | 9/4 = 2 1/4 |
The last row shows a mixed number entering the sum: 2 3/4 becomes 11/4 first, because2 × 4 + 3 = 11. Everything after that is ordinary fraction arithmetic.
Working with two mixed numbers throughout? The Mixed Number Calculator keeps the whole-number part visible in both inputs and the answer.
Frequently asked questions
How do I add fractions with different denominators?
Rewrite both over a common denominator, then add the numerators and leave the denominator alone. For 3/4 + 1/3 the common denominator is 12, giving 9/12 + 4/12 = 13/12. The calculator shows that middle step, because it is the one that gets skipped.
How do I multiply and divide fractions?
To multiply, multiply the numerators together and the denominators together: 2/3 × 5/6 = 10/18, which reduces to 5/9. To divide, flip the second fraction and multiply instead: 1/2 ÷ 3/5 becomes 1/2 × 5/3 = 5/6. Neither needs a common denominator.
Can I enter mixed numbers and whole numbers?
Yes. Type a mixed number with a space, as in 2 3/4, and a whole number on its own. A whole number is treated as itself over 1, which is why 3 × 5/7 works out as 3/1 × 5/7 = 15/7.
Why is my answer shown as a different fraction from the one I expected?
Because it is reduced to lowest terms. 10/18 and 5/9 are the same number, and the calculator always shows the simplest form. The working line keeps the unreduced version so you can see where the answer came from.
Are the results exact?
Yes. The sum is done in whole numbers, not decimals, so 1/3 + 1/6 comes out as exactly 1/2. Floating-point arithmetic cannot represent a third, which is why a fraction calculator has to work this way rather than converting first.
What happens if I divide by zero?
The result reads "—" and the working line says "Cannot divide by zero". Dividing by zero has no answer, and a calculator that returned a number there would be wrong rather than helpful. Enter a non-zero second fraction and the answer reappears.
Last updated 25 October 2026.