How to use
- Choose add, subtract, multiply, or divide.
- Enter the first fraction as numerator over denominator.
- Enter the second fraction the same way. Use a negative numerator for a negative fraction.
- Press Calculate. The hero shows the reduced fraction and a decimal beside it.
How it's calculated
Addition and subtraction use a common denominator: a/b + c/d = (ad + bc) / bd, and subtraction flips the sign in the middle. Multiplication is (a×c) / (b×d). Division by c/d is multiplication by d/c.
The greatest common divisor of the numerator and the denominator then divides both, so 2/4 becomes 1/2. A negative sign is kept on the numerator.
Worked example
1/2 + 1/3 = (3 + 2) / 6 = 5/6, which is about 0.833. 1/2 ÷ 1/4 = 1/2 × 4/1 = 2/1. Subtracting 3/4 from 1/2 gives (2 − 3) / 4 = −1/4.
Assumptions
Integers in all four boxes. A zero denominator is rejected. Dividing by a zero numerator is rejected. The decimal is the reduced fraction as a number, not a rounded measurement.
FAQ
How do I enter a mixed number?
Convert it first. 2 1/4 is 9/4. The page does not have a whole-number box.
Can denominators be negative?
Yes. The reducer moves a negative sign onto the numerator so the denominator is shown positive.
What is lowest terms?
Numerator and denominator have been divided by the largest integer that goes into both.
Does this handle decimals inside a fraction?
The boxes accept numbers, but the reducer uses integer arithmetic. Use whole numerators and denominators.