Fraction Calculator
Fraction arithmetic has exactly four rules, but they are easy to misremember under pressure. This fraction calculator adds, subtracts, multiplies and divides any two fractions, then simplifies the result to its lowest terms and shows the decimal and percentage equivalents.
Enter numerators and denominators, pick the operation, and read the simplified result — negative values are handled too.
Enter valid values to see the results.
Formula
Addition and subtraction need a common denominator (multiply each fraction by the other’s denominator). Multiplication is straight across. Division flips the second fraction and multiplies. Every result is then reduced by the greatest common divisor.
What you need
- Enter the first fraction as numerator over denominator, then the second.
- Denominators cannot be zero; for division, the second numerator cannot be zero either.
- Whole numbers are fractions with denominator 1: 3 = 3/1.
Worked example
Practical tips
- To compare fractions quickly, convert both to decimals or cross-multiply: a/b vs c/d compares ad vs bc.
- Simplify before multiplying large fractions — cancel common factors early to keep numbers small.
- A mixed number like 1¾ is 7/4: multiply the whole part by the denominator and add the numerator.
- Dividing by a fraction always means multiplying by its reciprocal — “keep, change, flip”.
Common fraction–decimal–percentage equivalents
| Fraction | Decimal | Percentage |
|---|---|---|
| 1/4 | 0.25 | 25% |
| 1/3 | 0.3333 | 33.33% |
| 1/2 | 0.5 | 50% |
| 3/4 | 0.75 | 75% |
Common mistakes
- 1 Adding numerators and denominators straight across: 1/2 + 1/3 is not 2/5.
- 2 Forgetting to flip the second fraction when dividing.
- 3 Leaving results unsimplified: 9/12 should be reported as 3/4.
Frequently asked questions
How do I add fractions with different denominators?
Find a common denominator — multiplying the two denominators always works — convert both fractions, then add the numerators: 1/2 + 1/3 = 3/6 + 2/6 = 5/6.
How do I divide fractions?
Multiply the first fraction by the reciprocal of the second: 3/4 ÷ 2/3 = 3/4 × 3/2 = 9/8.
How do I convert a fraction to a decimal?
Divide the numerator by the denominator: 3/8 = 3 ÷ 8 = 0.375. This calculator shows the decimal automatically.
What does it mean to simplify a fraction?
Divide numerator and denominator by their greatest common divisor so the fraction is in lowest terms: 9/12 → 3/4. The value is unchanged.