GCF Calculator
Find the greatest common factor of two or more numbers, with prime factorisations shown so you can see exactly where the answer comes from.
How to use it
- Type the numbers separated by commas, spaces or new lines.
- The prime factorisation of each number is listed underneath the answer.
- The LCM is shown at the same time, since the two go together.
Examples
| 12, 18, 30 | GCF 6 |
| 48, 180 | GCF 12 |
The greatest common factor is the largest number that divides every number in the list with nothing left over. It answers a specific practical question: what is the biggest identical group I can split things into?
Give it two or more numbers and it lists the prime factorisation of each, then shows exactly which shared primes make up the GCF — so the answer is not just a number but a visible reason.
Worked example
A party planner has 24 chocolates and 36 candies and wants to make identical favour bags with no leftovers. GCF(24, 36) = 12, so 12 bags is the most that can be made, each with 2 chocolates and 3 candies. Any number of bags that doesn't divide both 24 and 36 leaves some sweets over.
GCF and simplifying fractions
To reduce a fraction to lowest terms, divide the numerator and denominator by their GCF. 48/180 simplifies by dividing both by GCF(48, 180) = 12, giving 4/15 in one step instead of several rounds of trial division.
Questions people ask
Is GCF the same as HCF and GCD?
Yes. Greatest common factor, highest common factor and greatest common divisor are three names for the same thing.
How are the GCF and LCM related?
For any two numbers, GCF × LCM equals the product of the numbers. That check is shown under the result.
Is anything sent to a server?
No. Every calculation runs in your browser, so nothing you type is uploaded and the page keeps working offline once it has loaded.
Last updated 17 August 2026