Fraction Calculator
Add, subtract, multiply or divide two fractions and get the exact answer in lowest terms, with the mixed number and decimal. Negative and improper fractions work too.
Runs in your browser. Your data is not uploaded.How our tools work
How do I add, subtract, multiply or divide fractions?
Enter two fractions and choose add, subtract, multiply or divide. The answer is exact and in lowest terms, with its decimal value and, for an improper fraction, the mixed number: 1/2 + 1/4 = 3/4, and 7/4 is 1 3/4. Negative fractions work too. Enter a mixed number as an improper fraction: 1 1/2 is 3/2.
Formulas & Methods
Add
Example: 1/2 + 1/4 = (4 + 2) ÷ 8 = 6/8 = 3/4
Subtract
Example: 3/4 − 1/2 = (6 − 4) ÷ 8 = 2/8 = 1/4
Multiply
Example: 2/3 × 3/4 = 6/12 = 1/2
Divide
Example: 1/2 ÷ 1/4 = 4/2 = 2
Key features
Lowest terms
Every result is simplified with the greatest common divisor, and the minus sign is kept on the top.
Mixed numbers and decimals
Improper results such as 7/4 are also shown as 1 3/4, with a decimal for reference.
Example: adding inch measurements
Fractions of an inch are where this comes up most. A 3/8 in board with a 5/16 in gap: enter 3/8 + 5/16. The common denominator is 16, so it is 6/16 + 5/16 = 11/16 in, or 0.6875 in as a decimal. Tape measures mark sixteenths, so 11/16 can be read straight off one.
Fraction, decimal or percentage?
Keep fractions while you are still calculating with thirds, sixths, sevenths and the like. A fraction whose denominator, in lowest terms, has a prime factor other than 2 or 5 has a decimal that never ends, such as 1/3 = 0.333… or 1/7 = 0.142857…, so any decimal you write down is rounded. Rounded decimals drift: 0.33 + 0.33 + 0.33 is 0.99, while 1/3 + 1/3 + 1/3 is exactly 1.
Switch to a decimal at the end, when you measure with a metric ruler, type the value into a spreadsheet or pay an amount of money. Use percentages to compare shares of different totals: 3/8 and 7/20 are hard to compare as fractions, but as 37.5% and 35% the larger one is obvious.
Frequently Asked Questions
How large can the numbers be?
Each numerator or denominator can have up to 15 digits. The maths uses whole numbers only, with no floating point, so the result stays exact even when the products along the way are much larger than that.
How do I turn a mixed number into an improper fraction?
Multiply the whole number by the denominator and add the numerator: 2 3/4 is (2 × 4 + 3)/4 = 11/4. The calculator has no box for whole numbers, so enter mixed numbers this way; an improper result is shown as a mixed number too.
Why can’t the denominator be zero?
A fraction divides the top by the bottom, and dividing by zero has no answer. The calculator points out a zero denominator instead.
How are negative fractions shown?
With the minus sign on the numerator: −1/2, never 1/−2. Two negatives make a positive.
Last updated: