Math
GCF and LCM Calculator
Use this calculator to find the GCF for simplifying and the LCM for common denominators or repeating cycles.
Separate numbers with commas, spaces, or semicolons.
Try an example
Result
GCF
—
- LCM
- —
- Count
- —
Student quick launch
Grade planning, algebra checks, and formulas students reach for most.
Study path
Use this calculator with
Follow these when you want the formula behind the answer, a short lesson, or nearby tools in the same topic.
What the gcf and lcm calculator solves
Use this calculator to find the The largest number that divides evenly into every number in a set. for simplifying and the LCM for common The bottom number of a fraction; it says how many equal parts make one whole. or repeating cycles.
Formula
How to use it
- Enter positive whole numbers.
- Use GCF to simplify or factor.
- Use LCM for common denominators and shared cycles.
How to read the answer
GCF shows the largest exact grouping size. LCM shows the first positive number all inputs divide into.
Common mistakes and edge cases
- Use whole numbers only.
- GCF cannot be larger than the smallest input.
- LCM can get large quickly when numbers share few factors.
Worked examples
Three numbers
GCF
6
Common denominator
GCF
4
Frequently asked questions
When do I use GCF?+
Use GCF to simplify fractions or factor expressions.
When do I use LCM?+
Use LCM to find common denominators or the first time repeating events line up.
About this calculator
- Written by
- mathcheck editorial team
- Last reviewed
- May 8, 2026
Method
- Uses the values entered by the user and stable formulas documented on the page.
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Last updated: May 8, 2026