GCD & LCM Calculator
Find the greatest common divisor and lowest common multiple of several numbers.
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How to use the gcd & lcm calculator
- Fill in the fields — they start with a worked example.
- Read the answer, and the arithmetic shown beneath it.
- Copy the results, or adjust the inputs to compare scenarios.
About this tool
The greatest common divisor is the largest number dividing all of them — what you divide by to simplify a fraction. The lowest common multiple is the smallest number they all divide into, which is what you need as a common denominator.
They are linked: for two numbers, GCD × LCM equals their product. That identity is how the LCM is calculated here without factorising anything.
Common uses
- Simplifying a fraction to lowest terms.
- Finding a common denominator.
- Working out when two repeating cycles coincide.
Frequently asked questions
- What is the GCD used for?
- Chiefly simplifying fractions and ratios — dividing both parts by the GCD gives the lowest terms in one step.
- How is the LCM calculated?
- Via the identity GCD × LCM = the product of the two numbers, applied pairwise across the list. It is faster and more reliable than factorising.
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