GCF and LCM Calculator

GCF and LCM Calculator finds the greatest common factor and the lowest common multiple of any list of whole numbers, and shows the prime factorisation of each one so you can see where both answers come from. The greatest common factor, also called the highest common factor, is the product of the primes they all share at the lowest power each appears to; the lowest common multiple takes every prime at its highest power.

Those two definitions are why the pair of numbers matters. Forty-eight is 2^4 x 3 and thirty-six is 2^2 x 3^2. They share 2^2 x 3, which is twelve, so that is the GCF. Taking the higher power of each gives 2^4 x 3^2, which is 144, the LCM. The factorisation table makes this checkable rather than something to accept.

For exactly two numbers there is a useful identity: the GCF times the LCM equals the product of the two numbers. It is shown when you enter a pair, both as a check on the answer and because it is the fastest way to get the LCM once you have the GCF.

The page shows its working, not just its answer. Where there is a formula it is printed with your own numbers substituted in, so you can check the result rather than take it on trust -- which is the difference between a calculator you can use for something that matters and one you cannot.

Everything runs inside your browser. What you type is never uploaded, never logged and never stored, and the calculator keeps working if your connection drops after the page has loaded.

• Shows greatest common factor, lowest common multiple, numbers given, coprime and gcf x lcm together, so you are not running it twice
• A results table you can read across
• Prints the formula with your own figures substituted in
• Updates as you type, with no button to press and no page reload
• Copy the result in one click
• Free, no sign-up, and it runs entirely in your browser

The gcf and lcm calculator is used by writers, developers, students, marketers and anyone else who needs the job done once without installing software. Common cases include:

• Simplifying a fraction to its lowest terms
• Finding a common denominator for several fractions
• Working out when two repeating events coincide
• Checking a factorisation in homework