Fraction Calculator
Add, subtract, multiply and divide fractions, with simplified, mixed and decimal answers.
Result (simplified)
17/12
- Mixed number
- 1 5/12
- Decimal
- 1.41666667
Enter two fractions, choose an operation and get the result as a simplified fraction, a mixed number and a decimal. Whole numbers work too: write 3 as 3/1.
The steps are shown so you can follow the method, which is useful for homework and for checking hand calculations.
How fraction calculator works
Adding and subtracting need a common denominator: cross-multiply, then combine the numerators. Multiplying multiplies across the tops and bottoms. Dividing multiplies by the reciprocal of the second fraction.
The answer is then reduced by dividing the numerator and denominator by their greatest common divisor.
The formula
a/b + c/d = (ad + bc) ÷ bd
a/b − c/d = (ad − bc) ÷ bd
a/b × c/d = ac ÷ bd
a/b ÷ c/d = ad ÷ bcWorked example: adding 2/3 and 3/4
Cross-multiply: 2 × 4 + 3 × 3 = 17 on top, and 3 × 4 = 12 underneath.
17/12 cannot be reduced further.
As a mixed number it is 1 5/12, and as a decimal 1.4167.
Dividing 3/5 by 9/10 flips the second fraction: 3/5 × 10/9 = 30/45 = 2/3.
When to use this tool
- Checking maths homework and exam practice.
- Combining measurements in cooking or woodworking, such as 3/4 cup plus 2/3 cup.
- Scaling a recipe by a fractional amount.
- Converting an awkward fraction into a decimal.
Common mistakes to avoid
- Adding numerators and denominators straight across: 1/2 + 1/3 is not 2/5.
- Forgetting to flip the second fraction when dividing.
- Leaving an answer unsimplified. 6/8 should be given as 3/4.
- Using zero as a denominator. It is undefined and the tool will flag it.
Frequently asked questions
- How do I add fractions with different denominators?
- Find a common denominator, convert each fraction, then add the numerators. Cross-multiplication gives a common denominator automatically.
- How do I divide fractions?
- Multiply the first fraction by the reciprocal of the second. Dividing by 9/10 is the same as multiplying by 10/9.
- How do I simplify a fraction?
- Divide the top and bottom by their greatest common divisor. 30/45 divides by 15 to give 2/3.
- How do I turn a fraction into a decimal?
- Divide the numerator by the denominator. 17 ÷ 12 is about 1.4167.
Learn more
- Guide · September 19, 2026How to Add, Subtract, Multiply and Divide Fractions
- Guide · September 19, 2026How to Simplify a Ratio and Solve Proportions
- Guide · September 19, 2026How to Calculate the Average (Mean, Median and Mode)
- Article · September 19, 2026Mean, Median or Mode: Which Average Should You Use?
Related tools
- Average CalculatorMean, median, mode, range and standard deviation for any list of numbers.
- Ratio CalculatorSimplify a ratio or solve a proportion such as 3:4 = x:20.
- Percentage CalculatorFind X% of a number, what percent one number is of another, or the total behind a percentage.
- Percentage Increase CalculatorFind the percentage increase between two numbers, or raise a number by a percentage.
- Percentage Decrease CalculatorFind the percentage decrease between two numbers, or reduce a number by a percentage.
- Percentage Difference CalculatorCompare two numbers as a percentage when neither one is the starting point.
Results are for information only and are not financial, legal or medical advice. The calculation logic is covered by automated tests, and examples on this page are worked out and re-checked before publishing. Spotted a mistake? Tell us.