Ratio Simplifier
Enter two whole numbers to simplify the ratio a:b to its lowest terms.
How ratio simplification works
A ratio is simplified by dividing both numbers by their greatest common divisor (GCD) — the largest number that divides both evenly. For example, 12:18 simplifies to 2:3, since 6 is the GCD of 12 and 18 (12÷6=2, 18÷6=3).
A ratio simplified to lowest terms can't be reduced further, since the two resulting numbers share no common factors other than 1. The decimal equivalent (a divided by b) gives the same relationship as a single number, useful for comparing ratios directly.
Frequently asked questions
What does it mean for a ratio to be in "lowest terms"?
A ratio is in lowest terms when the two numbers have no common factors left to divide out — their greatest common divisor is 1.
Is a ratio the same as a fraction?
They're closely related — a ratio a:b can be written as the fraction a/b, and simplifying a ratio uses the exact same process (dividing by the GCD) as simplifying a fraction.
What if my ratio has a decimal number, like 2.5:5?
This calculator works with whole numbers — multiply both sides by enough to clear any decimals first (e.g. 2.5:5 becomes 25:50) before simplifying.