Add or subtract two fractions and get the exact reduced result plus a decimal value.
Last updated: August 2026 | By Summa Calculator
Fractions can be added or subtracted directly only after they represent equal-sized parts. That means the denominators must match.
The only difference between the two formulas is whether the cross-products in the numerator are added or subtracted.
Addition is commutative, so swapping the fractions does not change the sum. Subtraction is different: the first fraction is the amount you start with, and the second is the amount being removed.
A negative subtraction result is valid; it means the second value exceeded the first.
A minus sign may appear in the numerator or denominator. One negative sign makes the fraction negative; two negative signs make it positive.
The calculator accepts either sign placement and normalizes the final reduced result so its denominator is positive.
Subtract 1/4 from 5/6:
The exact result is 7/12. Its decimal approximation is 0.58333333.
When should I use this instead of the adding-only calculator?
Use this calculator when you need both addition and subtraction in one tool or specifically need fraction subtraction.
Does switching operations keep my old values?
No. Changing between Add and Subtract resets the fraction inputs so a result from the previous mode cannot remain in view.
Does the answer reduce automatically?
Yes. The exact result is divided by the greatest common divisor and displayed with a positive denominator.
Does it multiply or divide fractions?
No. This calculator is limited to addition and subtraction.
Related Tools