Adding Fractions Calculator
Add two fractions and see the common denominator, the addition and the simplified answer — plus the decimal, percentage and mixed-number forms.
How to use it
- Type the numerator and denominator of each fraction.
- The answer is simplified automatically and shown as a decimal, a percentage and a mixed number.
- The working underneath is the same method you would use on paper.
Examples
| 1/2 + 1/3 | 5/6 |
| 3/4 + 5/6 | 19/12 |
Adding fractions means rewriting both over a common denominator first, then adding the numerators: a/b + c/d = (ad + cb) / bd. Skipping the common-denominator step is the single most common fraction mistake — adding numerators and denominators straight across gives a wrong, meaningless result.
Worked example — combining recipe measurements
A recipe calls for 1/2 cup of one ingredient in the base and 1/3 cup added later. Combined: 1/2 + 1/3 = (1×3 + 1×2) / (2×3) = 5/6 cup total — not 2/5, which is the wrong answer you get by adding across without a common denominator.
Questions people ask
Why do I need a common denominator?
Because fractions with different denominators are counting different-sized pieces. Rewriting both over the same denominator makes the pieces comparable, so the numerators can simply be added.
Is anything sent to a server?
No. Every calculation runs in your browser, so nothing you type is uploaded and the page keeps working offline once it has loaded.
Last updated 22 August 2026