Fraction arithmetic in brief
To add or subtract, give both fractions a common denominator: 1/2 + 3/4 = 2/4 + 3/4 = 5/4. To multiply, multiply the tops and the bottoms: 2/3 × 3/5 = 6/15 = 2/5. To divide, multiply by the reciprocal: 2/3 ÷ 4/9 = 2/3 × 9/4 = 18/12 = 3/2. Finally, simplify by dividing the top and bottom by their greatest common factor.
A result like 5/4 is an improper fraction; as a mixed number it is 1 1/4, and as a decimal 1.25. Recipes and measurements in inches often use mixed numbers; maths classes usually want improper fractions in lowest terms.
Worked example
1 1/2 × 2/3: write 1 1/2 as 3/2, multiply 3/2 × 2/3 = 6/6, which simplifies to 1.
You can also type decimals: 0.25 + 1/4 = 1/2.
How this works
The page converts each input into an exact fraction of two whole numbers: mixed numbers become improper fractions, and decimals become a number over a power of ten (0.75 = 75/100). It then applies the operation with exact integer arithmetic, without ever converting to floating point, and reduces the result by dividing numerator and denominator by their greatest common divisor. The answer is shown in lowest terms, as a mixed number and as a decimal. Everything runs in your browser.
Frequently asked
How do I write a mixed number?
With a space between the whole number and the fraction: 2 3/4.
How do I simplify a fraction?
Divide the top and bottom by their greatest common factor. The calculator always shows the simplest form.
Can I enter decimals?
Yes, finite decimals such as 0.75 or 2,5. For repeating decimals, type the fraction (1/3).
Why is the decimal rounded?
Fractions like 1/3 have endless decimals. The fraction result is exact; the decimal is for convenience.
Sources
Reviewed Oct 17, 2026 · test vectors fixtures/calculators/math/fraction-calculator/