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.
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 GCF for simplifying and the LCM for common denominators 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.
Related calculators
Prime Factorization Calculator
Factor a positive integer into primes and show the factor tree style division steps.
Fraction Calculator
Add, subtract, multiply, divide, simplify, compare, or convert decimals to fractions with steps and visual fraction bars.
Ratio Calculator
Simplify ratios, compare two quantities, and find unit rates with clear proportional reasoning steps.
Discount Calculator
Calculate sale price, stacked discounts, original price before a discount, or the discount percent between two prices.
Percentage Calculator
Calculate percent of a number, part-to-whole percentages, percent change, missing wholes, and reverse percent changes.
Slope Calculator
Find slope from two points or solve a missing coordinate from a known slope. Includes equations, intercepts, grade, graph, and step-by-step work.
Last updated: May 8, 2026