The Greatest Common Factor (GCF) or Greatest Common Divisor (GCD) is the largest whole number that divides equally into two or more numbers. For example, the factors of 12 are 1, 2, 3, 4, 6, and 12. The factors of 15 are 1, 3, 5, and 15. The GCF of 12 and 15 is 3 because it’s the largest number that’s a factor of 12 and 15.

The Least Common Multiple (LCM) is the smallest whole number that is evenly divisible by two or more numbers without leaving a remainder. For example, the multiples of 12 are 12, 24, 36, 48, 60, and so on. The multiples of 15 are 15, 30, 45, 60, and so on. The LCM of 12 and 15 is 60 because it’s the smallest number that’s a multiple of 12 and 15.

Use the calculator below to quickly calculate the greatest common factor and least common multiple of two numbers.

Greatest Common Factor and Least Common Multiple Calculator