Use this free online fraction calculator to add, subtract, multiply, or divide two fractions and get the answer in both simplified fraction and decimal form. Enter each numerator and denominator, choose an operation, and calculate instantly.
How to Use the Fraction Calculator
Enter the numerator and denominator for "Fraction 1".
Select an operation: addition (+), subtraction (−), multiplication (×), or division (÷).
Enter the numerator and denominator for "Fraction 2".
Click "Calculate" to see the simplified fraction and its decimal equivalent.
The Rules Behind Each Operation
For two fractions a/b and c/d, the calculator applies these rules and then reduces the answer to lowest terms:
Operation
Rule
Example
Add
(a × d + c × b) / (b × d)
3/4 + 5/6 = 38/24 = 19/12
Subtract
(a × d − c × b) / (b × d)
3/4 − 5/6 = −2/24 = −1/12
Multiply
(a × c) / (b × d)
3/4 × 5/6 = 15/24 = 5/8
Divide
(a × d) / (b × c): multiply by the flipped second fraction
3/4 ÷ 5/6 = 18/20 = 9/10
For addition and subtraction the tool multiplies the two denominators instead of hunting for the least common denominator. The unreduced fraction can therefore look large, but dividing by the greatest common divisor at the end gives the same final answer you would get by hand.
Worked Example with Mixed Numbers
A recipe needs 1½ cups of flour and you want to make two-thirds of it. The calculator works with simple fractions only, so first convert the mixed number: 1½ = (1 × 2 + 1)/2 = 3/2. Enter 3/2 × 2/3. The raw product is 6/6, which simplifies to 1/1, a decimal of 1. You need exactly one cup.
Answers are shown as improper fractions. To turn one into a mixed number, divide the numerator by the denominator: for 19/12, 19 ÷ 12 is 1 remainder 7, so the answer is 1 7/12. The decimal, 1.583333, is rounded to six places with trailing zeros removed.
Common Fraction Mistakes
Adding tops and bottoms directly. 1/2 + 1/3 is not 2/5; it is 5/6, because the parts must be the same size before you can add them.
Flipping the wrong fraction when dividing. Only the second fraction, the divisor, is inverted.
Typing a mixed number such as 2 1/4 into one box. Enter it as the improper fraction 9/4 instead.
Placing the minus sign inconsistently. The tool accepts a negative numerator or denominator and always moves the sign to the numerator in the answer, so 3/−4 is shown as −3/4.
Frequently Asked Questions
You can add, subtract, multiply, or divide two fractions by choosing the operation from the dropdown between Fraction 1 and Fraction 2.
After computing the raw numerator and denominator, the calculator finds their greatest common divisor (GCD) and divides both by it, keeping the denominator positive, so the fraction is always shown in its simplest form.
Convert it to an improper fraction first: multiply the whole number by the denominator and add the numerator. 2 3/4 becomes (2 × 4 + 3)/4 = 11/4, so enter 11 as the numerator and 4 as the denominator.
The calculator always gives the simplified fraction as numerator over denominator, along with its decimal value. To get a mixed number, divide: 19/12 is 1 with remainder 7, which is 1 7/12.
Some fractions, such as 1/3 or 5/12, have decimals that repeat forever. The calculator rounds the decimal to six places, so the fraction result is the exact one and the decimal is an approximation.