🧮 เครื่องคิดเลข GCD & LCM

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This calculator finds the greatest common divisor (GCD) — the largest number that divides all your values evenly — and the least common multiple (LCM), the smallest number they all divide into. Enter two or more whole numbers separated by commas or spaces and it also tells you whether they are coprime.

The GCD is found with the Euclidean algorithm: repeatedly replace the larger number with the remainder of dividing the two until one becomes zero; the other is the GCD. The LCM is then built up pairwise using LCM = a × b ÷ GCD. For 12, 18 and 24 the greatest common divisor is 6 and the least common multiple is 72. When the GCD is 1 the numbers share no common factor and are called coprime.

The GCD is what you use to reduce a fraction to lowest terms, while the LCM gives the common denominator for adding fractions and the period at which repeating cycles line up. The result is the same no matter what order you enter the numbers in.