Loading calculator...
- Adds, subtracts, multiplies and divides two fractions or mixed numbers.
- Gives the answer as a simplified fraction, a mixed number, a decimal and a percent.
- Shows every step: common denominator, rewriting, combining and simplifying.
- Works with negative values and catches mistakes such as a zero denominator.
How to use the fraction calculator
Enter the first fraction
Type the numerator (top number) and denominator (bottom number). For a mixed number such as 2 1/3, put 2 in the whole number box.
Pick the operation
Choose add, subtract, multiply or divide.
Enter the second fraction
Fill in its whole number (or leave 0), numerator and denominator.
Read the answer
The result updates instantly as a simplified fraction, mixed number, decimal and percent, with the full working below it.
How fractions are calculated
Every operation starts by turning mixed numbers into improper fractions. For 3 2/5, multiply the whole number by the denominator and add the numerator: 3 × 5 + 2 = 17, so 3 2/5 = 17/5. After that, each operation follows its own simple rule, and the last step is always to divide the top and bottom by their greatest common divisor so the answer is in lowest terms.
Adding and subtracting
a/b + c/d = (a × d/g + c × b/g) / LCD
LCD = least common denominator of b and d
The calculator uses the least common denominator rather than simply multiplying b × d, so the numbers stay small.
Multiplying and dividing
a/b × c/d = (a × c) / (b × d)
a/b ÷ c/d = a/b × d/c = (a × d) / (b × c)
To divide, flip the second fraction (take its reciprocal) and multiply. You cannot divide by a fraction equal to 0.
Example 1: adding 1/2 + 3/4
The denominators are 2 and 4, so the least common denominator is 4.
- Rewrite 1/2 2/4
- Add the numerators 2/4 + 3/4 = 5/4
- Mixed number 1 1/4
- Decimal 1.25
So 1/2 + 3/4 = 5/4, which is 1 1/4 or 1.25.
Example 2: adding mixed numbers 3 2/5 + 1 3/4
Convert both to improper fractions first.
- 3 2/5 17/5
- 1 3/4 7/4
- LCD of 5 and 4 20
- Rewrite 68/20 + 35/20
- Sum 103/20 = 5 3/20 = 5.15
The answer is already in lowest terms because 103 and 20 share no common factor.
Example 3: dividing 3/4 ÷ 2/5
Flip the second fraction and multiply.
- Reciprocal of 2/5 5/2
- Multiply 3/4 × 5/2 = 15/8
- Mixed number 1 7/8
- Decimal 1.875
Dividing by a fraction smaller than 1 always gives a bigger number than you started with.
Common fractions and their decimals
A quick reference for fractions you meet every day.
- 1/2 0.5 (50%)
- 1/3 0.3333… (33.33%)
- 1/4 0.25 (25%)
- 1/5 0.2 (20%)
- 1/8 0.125 (12.5%)
- 2/3 0.6667 (66.67%)
- 3/4 0.75 (75%)
Fractions whose denominator has only 2 and 5 as prime factors give decimals that end; others repeat forever.
Where a fraction calculator helps
Homework and tests
Check answers for fraction worksheets and see each step so you can spot where a mistake happened.
Cooking and baking
Scale recipes, such as 3/4 cup times 1 1/2, without guessing.
Woodwork and DIY
Add or subtract inch fractions such as 5/8 and 3/16 when measuring and cutting.
Everyday maths
Split bills, compare portions or convert a fraction into a percent in one click.
A fraction is in lowest terms when the numerator and denominator share no factor other than 1. The calculator divides both by their greatest common divisor, the same value you get from our GCD calculator. The common denominator it uses comes from the LCM calculator logic, and you can turn any answer into a percentage with the percentage calculator.
Fraction calculator FAQ
How do I enter a mixed number?
Put the whole part in the whole number box and the fraction part in the numerator and denominator boxes. For 2 1/3, enter 2, 1 and 3.
How do I enter a negative fraction?
Type a minus sign in the numerator, or in the whole number box for a negative mixed number. The calculator keeps the sign on the result.
Why is my answer shown as an improper fraction?
The headline shows the simplified fraction, which can be improper such as 5/4. The mixed number (1 1/4) and decimal are shown right under it.
Can I use decimals in the boxes?
No. Fractions use whole numbers on the top and bottom. Convert a decimal such as 0.75 to 75/100 first, or use the decimal result instead.
What happens if the denominator is 0?
A fraction with a zero denominator is undefined, so the calculator shows a message instead of a result.
Is the result always simplified?
Yes. Every answer is reduced to lowest terms by dividing the numerator and denominator by their greatest common divisor.