Fraction Calculator
Add, subtract, multiply and divide fractions and mixed numbers, with the answer simplified and every step shown.
Exact integer arithmetic · By Stuart Mathieson · Updated October 2026
Results
Answer
Mixed Number
Decimal
Steps
Decimals are rounded to 6 places; the fraction is exact.
How to work with fractions
A fraction is a numerator (the top number) divided by a denominator (the bottom number). A mixed number like 2 1/3 is a whole number plus a fraction - the calculator turns it into an improper fraction first: 2 1/3 = (2 × 3 + 1) / 3 = 7/3.
Adding and subtracting
Fractions can only be added or subtracted when they share a denominator. The calculator uses the lowest common denominator - the least common multiple of the two denominators - then adds or subtracts the numerators:
Multiplying
Multiply the numerators together and the denominators together:
Dividing
Dividing by a fraction is the same as multiplying by its reciprocal - the fraction turned upside down:
Simplifying
A fraction is in its simplest form when the numerator and denominator have no common factor other than 1. To simplify, divide both by their greatest common divisor (GCD): 21/12 has a GCD of 3, so it becomes 7/4. The calculator finds the GCD with Euclid's algorithm, and works in whole numbers throughout, so the fraction it gives is exact - there's no rounding until the decimal.
Negative numbers and mixed numbers
- Put the minus sign on the whole number or the numerator: -2 1/3 means -(2 + 1/3) = -7/3.
- A negative denominator is fine too - the calculator moves the sign to the top, so 1/-4 becomes -1/4.
- To enter a whole number on its own, such as 5, type it in the whole number box and set the denominator to 1.
- Decimals can be written as fractions first: 0.75 = 75/100 = 3/4. To turn a fraction into a percentage, see the Percentage Calculator.
Frequently asked questions
How do you add fractions with different denominators?
Rewrite both fractions over a common denominator, then add the numerators. For 1/2 + 1/3 the lowest common denominator is 6, so 3/6 + 2/6 = 5/6.
How do you divide fractions?
Multiply the first fraction by the reciprocal of the second - flip the second fraction upside down. 3/4 ÷ 2/5 = 3/4 × 5/2 = 15/8, or 1 7/8 as a mixed number.
How do you convert a mixed number to an improper fraction?
Multiply the whole number by the denominator, add the numerator, and keep the same denominator. 2 1/3 = (2 × 3 + 1)/3 = 7/3.
How do I simplify a fraction?
Divide the numerator and the denominator by their greatest common divisor. 21/12 has a greatest common divisor of 3, so it simplifies to 7/4.