How to use the adding fractions calculator
Type the fractions to add – choose How many for up to 5, tick Mixed numbers for values like 2 1/3 – and press Calculate. The answer comes in simplest form and as a mixed number, with every step of the working.
How to add fractions
Same denominators
Add the numerators and keep the denominator: the parts are the same size, so you just count them.
\frac{2}{7} + \frac{3}{7} = \frac{2 + 3}{7} = \frac{5}{7}Different denominators
- Find the least common denominator (LCD).
- Rewrite each fraction over the LCD.
- Add the numerators, keep the denominator.
- Simplify and write as a mixed number if it is more than 1.
Example: 1/4 + 2/3. The LCD of 4 and 3 is 12.
\frac{1}{4} + \frac{2}{3} = \frac{1 \times 3}{4 \times 3} + \frac{2 \times 4}{3 \times 4} = \frac{3}{12} + \frac{8}{12} = \frac{11}{12}Adding mixed numbers
Change them to improper fractions first, then add as above:
2\frac{1}{2} + 1\frac{2}{3} = \frac{5}{2} + \frac{5}{3} = \frac{15}{6} + \frac{10}{6} = \frac{25}{6} = 4\frac{1}{6}Or add the whole numbers and the fractions separately: 2 + 1 = 3 and 1/2 + 2/3 = 1 1/6, so 4 1/6.
Common mistakes
- Adding the denominators: 1/2 + 1/3 is not 2/5. The parts must be the same size first: 3/6 + 2/6 = 5/6.
- Forgetting to change the numerator when you change the denominator: 1/4 = 3/12, not 1/12.
- Not simplifying the answer: 2/8 + 4/8 = 6/8 = 3/4.
Worked examples
Frequently asked questions
How do you add fractions with different denominators?
Rewrite them over the least common denominator, add the numerators and keep the denominator: 1/4 + 2/3 = 3/12 + 8/12 = 11/12.
Do you add the denominators when adding fractions?
No. Only the numerators are added once the denominators are the same; the denominator stays.
How do you add three or more fractions?
Use one common denominator for all of them. Choose 3, 4 or 5 under How many and the calculator does this in one step.
How do you add mixed numbers?
Change them to improper fractions, add, then turn the answer back into a mixed number – or add the whole numbers and the fractions separately.
What is 1/2 + 1/3?
5/6, because 1/2 = 3/6 and 1/3 = 2/6.