Subtracting Fractions Calculator

Subtracting fractions uses the same machinery as adding them. The pieces have to be the same size before the numerators mean anything, so you find a common denominator, rewrite both fractions over it, and then take one numerator away from the other. Only two things separate subtraction from addition. The first is that order matters: 3/4 minus 1/2 is not the same as 1/2 minus 3/4, and entering the fractions in the wrong sequence flips the sign of your answer. The second is that the result can be negative, which is perfectly legal and often the correct answer to a real problem, but it surprises students who expect every fraction to sit between 0 and 1.

This calculator shows the entire route rather than just the difference. You get the least common denominator of the two fractions, what each one becomes when rewritten over it, the subtraction of the numerators, the reduced answer, and a mixed number when the result is larger than 1. It also checks itself in reverse by adding the second fraction back onto the answer, which should return the fraction you started with. Mixed numbers are supported once you convert them to improper fractions first, and doing it that way removes the need to borrow from the whole number, which is where most hand-written mixed number subtraction falls apart.