LCM & HCF Calculator
Find the Least Common Multiple and Highest Common Factor (GCD) of two or three numbers, with the relationship between them.
HCF (GCD)
—
LCM —
Check: HCF × LCM —
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How it works
HCF by Euclid's algorithm; LCM = product ÷ HCFFrequently Asked Questions
What is the difference between LCM and HCF?
HCF (highest common factor, or GCD) is the largest number that divides all of them; LCM (least common multiple) is the smallest number they all divide into. For 12 and 18, HCF = 6 and LCM = 36.
How do I find the HCF quickly?
Euclid's algorithm: repeatedly replace the larger number with its remainder when divided by the smaller, until one becomes zero. It's what this calculator uses and is far faster than listing factors.
How are LCM and HCF related?
For two numbers, LCM × HCF = the product of the numbers. So once you have one, the other follows — 12 × 18 = 216 = 6 × 36.