Fraction Calculator
Add, subtract, multiply, or divide two fractions — with the answer simplified to lowest terms and shown as a decimal.
How fraction operations work
Multiply: (a/b) × (c/d) = ac/bd
Divide: (a/b) ÷ (c/d) = (a/b) × (d/c)
Simplify: divide top and bottom by their GCD
1/2 + 1/3: common denominator 6 → 3/6 + 2/6 = 5/6 ≈ 0.833.
A recipe calls for 3/4 cup of flour in one step and 2/3 cup more in another. Common denominator of 4 and 3 is 12: 3/4 = 9/12 and 2/3 = 8/12.
9/12 + 8/12 = 17/12, which simplifies to the mixed number 1 and 5/12 cups total — just over 1 3/8 cups, since 5/12 is slightly less than 6/12 (a half).
Fractions in practice
Fractions show up in recipes, measurements, and woodworking far more than decimals do. The two rules that matter: you can only add or subtract fractions once they share a denominator, and you should always simplify the answer (8/12 and 2/3 are the same number, but 2/3 is the accepted form). To turn a fraction into a percentage, divide and multiply by 100 — the percentage calculator does the rest. For ratios and scaling, see the ratio calculator.
Common fraction-to-decimal equivalents
| Fraction | Decimal |
|---|---|
| 1/8 | 0.125 |
| 1/4 | 0.25 |
| 1/3 | 0.333… |
| 1/2 | 0.5 |
| 2/3 | 0.667… |
| 3/4 | 0.75 |
| 5/8 | 0.625 |
Common fraction mistakes
- Adding or subtracting numerators without a common denominator first. 1/2 + 1/3 is not 2/5 — you must convert both to sixths (3/6 + 2/6) before combining.
- Comparing fractions by their numerators or denominators alone. 5/8 looks bigger than 2/3 at a glance, but converting both to twenty-fourths (15/24 vs. 16/24) shows 2/3 is actually larger.
- Forgetting to simplify the final answer. 17/12 and 1 5/12 are the same value, but leaving an answer unsimplified or as an improper fraction makes it harder to use in a recipe or measurement.
Kitchen scales complicate fraction math further, since most U.S. measuring cups only mark halves, thirds, and quarters rather than arbitrary denominators like twelfths. When a calculation produces an awkward fraction such as 5/12 cup, the practical move is to convert to tablespoons instead: since 1 cup equals 16 tablespoons, 5/12 cup is 5/12 × 16 ≈ 6.67 tablespoons, or about 6 and 2/3 tablespoons — a measurement most kitchen tablespoons can actually approximate, unlike a twelfth of a cup.
Frequently asked questions
How do you add fractions?
Common denominator, add numerators, simplify. 1/2 + 1/3 = 5/6.
How do you multiply and divide fractions?
Multiply straight across; to divide, flip the second and multiply.
How do you simplify a fraction?
Divide top and bottom by their greatest common divisor. 8/12 → 2/3.
How do I convert a fraction to a decimal or percentage?
Divide the numerator by the denominator for the decimal (1/2 = 0.5), then multiply by 100 for the percentage (50%). This calculator shows the decimal form automatically alongside the simplified fraction.
How do I add fractions with different denominators using measuring cups?
Convert to a common denominator, then add numerators. 3/4 cup + 2/3 cup = 9/12 + 8/12 = 17/12, or 1 5/12 cups.
How do you compare two fractions to see which is larger?
Convert both to a common denominator or to decimals. 5/8 vs. 2/3 → 15/24 vs. 16/24 → 2/3 is larger.
Related calculators
Last reviewed: September 2026.