MATH TOOL
GCD / LCM Calculator
Find the greatest common divisor and least common multiple of two or more numbers.
GCD (Greatest Common Divisor)
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LCM (Least Common Multiple)
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About this tool
Find the greatest common divisor and least common multiple of two or more whole numbers — useful for simplifying fractions to lowest terms, finding a common denominator, or solving classic scheduling/repeating-cycle math problems.
Frequently asked questions
- What is GCD used for?
- The GCD (also called GCF, greatest common factor) is the largest number that divides all your inputs evenly — it's exactly what you divide a fraction's numerator and denominator by to simplify it to lowest terms.
- What is LCM used for?
- The LCM is the smallest number that all your inputs divide into evenly — commonly needed to find a common denominator when adding or comparing fractions, or to figure out when repeating events (like two blinking lights) line up again.
- How is this calculated for more than two numbers?
- Using the Euclidean algorithm pairwise: GCD(a,b,c) = GCD(GCD(a,b),c), and similarly for LCM, which extends cleanly to any number of inputs.