Simplify a ratio to lowest terms, or solve for the missing term in a proportion A:B = C:D.
Both A and B are divided by their greatest common divisor (GCD), the same way a fraction is reduced — e.g. 8:12 shares a GCD of 4, simplifying to 2:3.
It uses cross-multiplication: in a true proportion, A × D = B × C. Fill in any 3 of the 4 fields and the calculator rearranges that equation to solve for whichever one you left blank.
They express each side of the ratio as a share of the combined total — useful for splitting a quantity in a given ratio, e.g. a 2:3 ratio is 40% and 60% of the whole.