Decimal
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Math · Fractions
Fraction
Fraction
calculator
Add, subtract, multiply or divide two fractions. The answer comes back reduced to lowest terms, with the decimal alongside it, the instant you change a number.
Two-fraction arithmetic
lowest terms
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Before simplifying
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Doing it by hand too?
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How fraction arithmetic works
Every operation on two fractions follows a fixed recipe, then the answer is reduced to lowest terms by dividing top and bottom by their greatest common divisor.
Add or subtract
a/b ± c/d = (a·d ± c·b) / (b·d)
Multiply
a/b × c/d = (a·c) / (b·d)
Divide
a/b ÷ c/d = (a·d) / (b·c)
Common denominators
Adding and subtracting need a shared bottom number. The quickest reliable way is to multiply the two denominators together (b·d), rescale both numerators to match, then combine. The result may not be in lowest terms yet, that's the next step.
Simplifying
½ + ⅓
1·3 + 1·2 = 5 over 2·3 = 6
gcd(5, 6) = 1 → already lowest terms = 5/6
gcd(5, 6) = 1 → already lowest terms = 5/6
The calculator always reduces the answer and, if it comes out to a whole number, shows just that. It also gives the decimal, so the percentage calculator is one step away if you need a percent.
Common questions
Fraction FAQ
Give them a common denominator by multiplying the two bottoms together, rescale each top to match, add the tops, then reduce. For ½ + ⅓: (1·3 + 1·2) ÷ (2·3) = 5/6.
To multiply, multiply the tops together and the bottoms together. To divide, flip the second fraction and multiply. Both answers are then reduced to lowest terms.
Reducing it to lowest terms, dividing the numerator and denominator by their greatest common divisor so no smaller equivalent exists. 6/8 simplifies to 3/4.
Yes. Enter a negative on either number. The calculator keeps the sign on the numerator and simplifies as normal.
Yes. Alongside the reduced fraction it shows the decimal equivalent, so you can use whichever form you need.