How fraction arithmetic works
Addition & Subtraction
a/b ± c/d = (a×d ± c×b) / (b×d) Multiplication
a/b × c/d = (a×c) / (b×d) Division
a/b ÷ c/d = a/b × d/c = (a×d) / (b×c) Every result is automatically reduced to lowest terms. When a result is larger than 1, both the improper-fraction form (like 15/4) and the equivalent mixed-number form (like 3¾) are shown together.
Frequently asked questions
How do you add fractions with different denominators?
Cross-multiply to get a common denominator: a/b + c/d becomes (a×d + c×b) over (b×d), then simplify the result. For example, 1/2 + 1/3 = (1×3 + 1×2)/(2×3) = 5/6.
How do you divide fractions?
Multiply by the reciprocal of the second fraction — flip it upside down, then multiply straight across. 1/2 ÷ 1/4 becomes 1/2 × 4/1 = 2.
Can I use mixed numbers in the calculator?
Yes — enter a whole number in the small box to the left of each fraction. Leave it empty for a plain fraction with no whole-number part.