Fraction Calculator
Working with fractions by hand is where sign errors and forgotten simplifications creep in.
How to use
- Choose the operation: add, subtract, multiply or divide.
- Enter the numerator and denominator of fraction A, then of fraction B.
- Read the simplified result instantly, with its decimal approximation underneath.
- Change any number and the answer updates at once; everything stays on your device.
Frequently asked questions
How are the fractions simplified?
Both operands are reduced first, then the result is reduced again by dividing out the greatest common divisor (Euclid's algorithm). The denominator is always kept positive, with any minus sign carried by the numerator.
What happens with a zero denominator?
A fraction with denominator 0 is not a number, so the tool reports an explicit error instead of pretending to compute. Division by a fraction whose numerator is 0 is likewise rejected as undefined.
Can I enter negative fractions?
Yes — put the minus sign on the numerator or the denominator, either works; the sign is normalised to the numerator automatically.
Are mixed numbers supported?
Not in this version. Convert first: 2 1/2 becomes 5/2 — enter 5 and 2 — and read the result back the same way whenever its numerator is larger than the denominator.
Is the decimal approximation exact?
No, and it is labelled as an approximation on purpose. Fractions like 1/3 have no finite decimal form; the fraction itself is the exact answer and the decimal is there for a quick sense of size.
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About this tool
Working with fractions by hand is where sign errors and forgotten simplifications creep in. This free fraction calculator performs the four operations — addition, subtraction, multiplication and division — on two fractions and returns the result fully simplified, with the smallest possible numerator and denominator, plus a decimal approximation so you can sanity-check the size at a glance. Everything is exact: the engine works on integer numerators and denominators (reducing with the greatest common divisor, the same Euclidean method taught in school), so 1/2 + 1/3 is exactly 5/6, never 0.8333333333 pretending to be the answer. It handles negative fractions in either operand, normalises signs so the denominator is always positive, and refuses the two operations that are genuinely undefined: a zero denominator and division by a zero fraction, telling you plainly what went wrong. Homework checks, recipe scaling, workshop measurements and exam revision all benefit. It computes as you type, entirely in your browser — no data ever leaves your device.