How to use it
- Pick an operation: calculate, simplify, or decimal to fraction.
- Enter numerators and denominators in the stacked boxes.
- Choose +, −, × or ÷.
- Read the simplified answer, the mixed number, the decimal and the steps.
How to use the fraction calculator
Type each fraction into the stacked boxes: numerator on top, denominator below. Leave a denominator empty to enter a whole number. Pick an operation and the answer appears right away, simplified to lowest terms, with the equivalent mixed number and decimal, plus the steps used to get there.
The Simplify tab reduces a single fraction, and Decimal to fraction converts values such as 0.375 into 3/8. Everything runs in your browser; nothing is uploaded.
The rules, with examples
Adding and subtracting: find a common denominator (the least common multiple of the denominators), rewrite both fractions, then add or subtract the numerators.
- 1/2 + 1/3 = 3/6 + 2/6 = 5/6
- 3/4 − 2/3 = 9/12 − 8/12 = 1/12
Multiplying: multiply the numerators and the denominators, then simplify.
- 2/3 × 9/10 = 18/30 = 3/5
Dividing: multiply by the reciprocal of the second fraction ("keep, change, flip").
- 5/6 ÷ 2/3 = 5/6 × 3/2 = 15/12 = 5/4 = 1 1/4
Simplifying fractions
A fraction is in lowest terms when the numerator and denominator have no common factor other than 1. To simplify, divide both by their greatest common factor (GCF).
Example: 18/24. The GCF of 18 and 24 is 6, so 18/24 = 3/4.
The calculator shows the GCF it used. For the GCF of larger numbers, with prime factorization and the Euclidean algorithm, use the GCF calculator; for common denominators, the LCM calculator.
Fractions and decimals for measurements
Tape measures and recipes in the U.S. use fractions, so converting between fractions and decimals comes up often:
| Fraction | Decimal |
|---|---|
| 1/16 | 0.0625 |
| 1/8 | 0.125 |
| 1/4 | 0.25 |
| 3/8 | 0.375 |
| 1/2 | 0.5 |
| 5/8 | 0.625 |
| 3/4 | 0.75 |
| 7/8 | 0.875 |
| 1/3 | 0.333… |
| 2/3 | 0.666… |
Decimal to fraction works exactly for up to 9 decimal places: 0.375 becomes 375/1000, which simplifies to 3/8. Repeating decimals such as 0.333… cannot be typed exactly, so 0.333 becomes 333/1000.
Mixed numbers and negative fractions
A mixed number combines a whole number and a proper fraction, such as 1 3/4. To enter one, convert it to an improper fraction first: multiply the whole number by the denominator and add the numerator. 1 3/4 = (1 × 4 + 3)/4 = 7/4. The calculator gives every improper result as a mixed number too.
For a negative fraction, put the minus sign in the numerator: −3/4. A negative denominator works as well; the result is always shown with the sign in front.
Recipe example: a recipe calls for 3/4 cup of sugar and you want 2 1/2 batches. 3/4 × 5/2 = 15/8 = 1 7/8 cups.
Common mistakes
- Adding denominators. 1/2 + 1/3 is not 2/5. Only the numerators are added, after the denominators are made equal.
- Forgetting to flip when dividing. Only the second fraction is inverted.
- Not simplifying. Teachers usually expect answers in lowest terms; 6/8 should be written as 3/4.
- Cancelling across addition. You can cancel common factors in a product, but not in a sum: (2 + 4)/2 is 3, not 4.
Frequently asked questions
How do you add fractions with different denominators?
Rewrite both fractions with a common denominator, usually the least common multiple, then add the numerators. 1/4 + 1/6 = 3/12 + 2/12 = 5/12.
How do I simplify a fraction?
Divide the numerator and denominator by their greatest common factor. 18/24 ÷ 6/6 = 3/4.
How do I divide fractions?
Multiply the first fraction by the reciprocal of the second: a/b ÷ c/d = a/b × d/c.
How do I convert a decimal to a fraction?
Write the decimal over the matching power of ten and simplify: 0.75 = 75/100 = 3/4. The Decimal to fraction tab does this for you.
Can I enter mixed numbers?
Convert them to improper fractions first (1 3/4 = 7/4). Results are shown both as an improper fraction and a mixed number.
Last updated: November 12, 2026