➗ Math
GCF and LCM Calculator
The greatest common factor is the largest number that divides all of them; the least common multiple is the smallest one they all divide. Euclid’s algorithm gets the first one in a handful of steps regardless of size, and the second follows from it directly because the product of two numbers equals their GCF times their LCM.
How it works
First number
Second number
Third number (0 to ignore)
Greatest common factor
Least common multiple
Simplified ratio
Common factors
Frequently asked questions
How do I use the GCF and LCM Calculator?
Fill in the fields above — the result recalculates instantly as you type. Everything runs in your browser, so the values you enter are never collected or stored.
Is this calculator free?
Yes. It is completely free, requires no account, and works on phones, tablets and desktops.