LCM/GCF Calculator
Free LCM and GCF calculator. Enter two or more numbers and get the least common multiple and greatest common factor instantly.
Runs entirely on your device - nothing is ever uploaded.
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How to use LCM/GCF Calculator
- Type two or more whole numbers, separated by commas.
- Read both answers together: the LCM for lining up, the GCF for splitting down.
- Apply them in turn - align denominators with the LCM, reduce the result with the GCF.
What it is for
Complete fraction workflows in one place: adding 5/12 + 7/18 needs the LCM (36) to combine and the GCF (1 here - already lowest) to finish. One run answers both halves instead of two separate calculations.
How it works
One pass computes both: the Euclidean algorithm finds the GCF across every number you enter, then the LCM follows from LCM × GCF = product of the pair. Both stay exact for whole numbers up to 15 digits.
How the LCM and GCF connect
For any pair, GCF × LCM equals the product of the numbers. With 12 and 18: GCF = 6 and LCM = 36, and 6 × 36 = 216 = 12 × 18. So finding one gives you the other for free - divide the product by the GCF to get the LCM. This calculator reports both together so fraction work flows: the LCM aligns denominators for adding, and the GCF reduces the answer back down.
Which one does your problem need
Ask when things line up or repeat - bus schedules, gear rotations, common denominators - and you want the LCM. Ask how to split, simplify, or factor evenly - tile sizes, fraction reduction, pulling factors from expressions - and you want the GCF. If a problem mentions both adding fractions and simplifying the result, run it here once and use each answer in turn.