Fraction Calculator
Add, subtract, multiply and divide two fractions, with the result fully simplified.
What the Fraction Calculator does
Fractions are added and subtracted over a common denominator, multiplied straight across, and divided by flipping the second fraction. The result is reduced by dividing both parts by their greatest common divisor.
Formula
a/b + c/d = (ad + cb) / bda/b − c/d = (ad − cb) / bda/b × c/d = ac / bda/b ÷ c/d = ad / bc
Inputs explained
| Input | Unit | Required | Notes |
|---|---|---|---|
| First numerator | number | Yes | — |
| First denominator | number | Yes | — |
| Operation | one of 4 options | Yes | — |
| Second numerator | number | Yes | — |
| Second denominator | number | Yes | — |
How to use it
- Choose Operation.
- Enter First numerator, First denominator, Second numerator and Second denominator.
- Select Calculate.
Worked example
A recipe needs 3/4 cup and you are adding another 2/3 cup.
- First fraction
- 3/4
- Operation
- Add
- Second fraction
- 2/3
3/4 + 2/3 = 17/12 = 1 5/12 ≈ 1.4167 cups.
Frequently asked questions
Why do I flip the second fraction when dividing?
Dividing by a number is the same as multiplying by its reciprocal. Dividing by 2/3 is multiplying by 3/2.
Can I enter negative fractions?
Yes. Put the minus sign on the numerator, for example −3 over 4.