Adding and Subtracting Fractions Calculator
The Adding and Subtracting Fractions Calculator combines two fractions using either addition or subtraction and returns the answer in lowest terms plus its decimal value. Choose the operation, enter each numerator and denominator, and it finds a common denominator and simplifies the result.
Formula
a/b ± c/d = (a×d ± c×b) / (b×d), then reduced
- Both fractions are placed over a common denominator (b × d), the numerators are added or subtracted, and the result is reduced to lowest terms.
- Addition: a/b + c/d = (a×d + c×b) / (b×d). Subtraction: a/b − c/d = (a×d − c×b) / (b×d).
- Negative results are allowed and the sign is shown on the numerator.
- Denominators must not be zero.
Example Calculation
Inputs
- First fraction — numerator: 3
- First fraction — denominator: 4
- Operation: subtract
- Second fraction — numerator: 1
- Second fraction — denominator: 2
Subtract 1/2 from 3/4: over a common denominator of 4 this is 3/4 − 2/4 = 1/4, or 0.25.
Frequently asked questions
How do you add or subtract fractions?
Put both fractions over a common denominator, then add or subtract the numerators and reduce. The calculator handles every step.
Can the result be negative?
Yes. If you subtract a larger fraction from a smaller one, the answer is negative and the sign is shown on the numerator.
Does it simplify the answer?
Yes. The result is always reduced to lowest terms using the greatest common divisor.
Can I switch between adding and subtracting?
Yes. Use the Operation selector to choose addition or subtraction.
What about different denominators?
No problem — the calculator automatically finds a common denominator before combining the fractions.