GCF LCM Calculator
Greatest Common Factor
Greatest Common Factor Runs locally in your browser
Two or more whole numbers separated by commas.
About the
The GCF and LCM Calculator finds the greatest common factor and the least common multiple of two or more whole numbers in one step. The greatest common factor is what you want when you are simplifying a ratio or a fraction; the least common multiple is what you want when you are adding fractions with different denominators or finding when two cycles line up. Both are reported together because they answer different halves of the same question.
Where people use the
- Simplifying a ratio or a fraction to its lowest terms.
- Finding a common denominator before adding fractions.
- Working out when two repeating schedules next coincide.
- Reducing a recipe or a mix ratio to smaller whole numbers.
How to use the
- 1
Enter the numbers
Two or more whole numbers separated by commas, for example 12, 18 or 24, 36, 60.
- 2
Run it
The greatest common factor and the least common multiple are reported for the whole set.
- 3
Use the GCF to simplify
Divide both parts of a ratio by the GCF to reduce it to its simplest form.
- 4
Use the LCM to align
The LCM is the smallest number every input divides into, which is the common denominator or the next alignment point.
Tips and best practices
- A GCF of 1 means the numbers share nothing; stop looking.
- Use the LCM as your common denominator when adding fractions.
- Whole numbers only; scale decimals up first.
Frequently asked questions
What is the difference between GCF and LCM?
The GCF is the largest number that divides all of them. The LCM is the smallest number that all of them divide into. One reduces, the other aligns.
Can I use more than two numbers?
Yes. Any number of values is accepted, and both results are computed across the whole set.
What if the numbers share no factor?
The GCF is 1, which means the numbers are coprime. The LCM is then simply their product.
Are decimals accepted?
No. Whole numbers only. Multiply decimals by a power of ten first if you need to.
What does a GCF of 1 mean for a fraction?
That the fraction is already in its simplest form. There is no number greater than 1 that divides both the numerator and the denominator.