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Fraction Calculator

Add, subtract, multiply, or divide two fractions. The answer is reduced for you, with the decimal alongside.

Fractions turn up in recipes, woodworking, schoolwork, and anywhere a quantity isn't a whole number. The four operations below cover the arithmetic that comes up most: adding and subtracting fractions (which needs a common denominator), and multiplying and dividing them (which doesn't). Every result is reduced to lowest terms and shown as both a fraction and a decimal. The calculation runs entirely in your browser and the formula is shown underneath so you can check the work by hand.

Add two fractions

+
Result
5/6= 0.833333

1/2 + 1/3 = 5/6

How to use

  1. Pick the operation

    The tabs across the top — Add, Subtract, Multiply, Divide — set which operation runs. Subtract and divide use the first fraction minus / divided by the second.

  2. Enter the two fractions

    Type a whole number into each numerator (top) and denominator (bottom) box. Negative numerators are allowed; denominators can't be zero. The result updates as you type.

  3. Read the answer

    The big tinted value is the result reduced to lowest terms, with the decimal next to it. The mono-spaced line shows the full expression that was evaluated.

Worked examples

ExpressionReducedDecimal
1/2 + 1/35/60.833333
3/4 − 1/41/20.5
2/3 × 3/41/20.5
(1/2) ÷ (1/4)2/12
2/4 (reduced)1/20.5

Frequently asked questions

How do I add two fractions by hand?
Give both fractions a common denominator, add the numerators, then reduce. 1/2 + 1/3 → 3/6 + 2/6 = 5/6. This calculator uses the cross-multiplication form, (a·d + c·b) / (b·d), then divides by the GCD to reduce.
What does "reduced to lowest terms" mean?
It means the numerator and denominator share no common factor other than 1. 2/4 reduces to 1/2 because both divide by 2. The calculator reduces every result automatically using the greatest common divisor.
How do I divide fractions?
Multiply the first fraction by the reciprocal (flip) of the second: (a/b) ÷ (c/d) = (a/b) × (d/c). So (1/2) ÷ (1/4) = (1/2) × (4/1) = 4/2 = 2/1.
Why does the result show a dash?
A dash appears when an input is invalid — a blank or non-integer field, a zero denominator, or an attempt to divide by a fraction equal to zero. Division by zero is undefined, so the calculator shows a dash instead of Infinity.
Can I enter negative fractions?
Yes. Put the minus sign on the numerator, e.g. −1 over 2. The result carries the sign on its numerator and always keeps the denominator positive, so −1/2 is shown rather than 1/−2.
Does the calculator store my data?
No. Every computation happens in your browser; nothing is sent to a server.

About

How reduction works

After each operation the raw numerator and denominator are divided by their greatest common divisor, found with Euclid's algorithm. The sign is normalized onto the numerator and the denominator is kept positive, so equivalent fractions always display in one canonical form.

Integer inputs only

The fields accept whole numbers so the arithmetic stays exact — no floating-point rounding creeps into the fraction itself. The decimal shown beside the result is computed from the reduced fraction and displays up to six decimal places with trailing zeros trimmed.

Sources & references

Authoritative references behind the math, constants, and tables on this page. Verified by Buğra Sözeri on the dates shown and re-checked at every deploy.