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Enter whole numbers
Add two or more numbers separated by commas, spaces, tabs, or new lines.
Free GCF Calculator
A GCF calculator finds the greatest common factor, or the largest whole number that divides evenly into every number in a set. Enter two or more whole numbers to see the GCF, common factors, and prime factorization steps.
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Math factor calculator
Enter two or more whole numbers
Teaching note
The calculator ignores signs when finding the GCF, because factors are usually taught as positive whole-number divisors.
GCF result
Greatest common factor: 6
3 numbers checked
Common factors
1, 2, 3, 6
Absolute values used
18, 24, 42
How the GCF is found
- 1. List the factors or prime factors for each number.
- 2. Find the factors that appear in every list.
- 3. Choose the largest shared factor: 6.
NumberPrime factors
182 x 3^2
242^3 x 3
422 x 3 x 7
NumberFactors
181, 2, 3, 6, 9, 18
241, 2, 3, 4, 6, 8, 12, 24
421, 2, 3, 6, 7, 14, 21, 42
How to Use This GCF Calculator
2
Review factors
Compare the factor lists and prime factors for each number.
3
Use the GCF
Copy or download the result for a lesson, worksheet, or homework check.
GCF Calculator FAQ
What is a GCF calculator?
A GCF calculator finds the greatest common factor, which is the largest whole number that divides evenly into every number you enter.
How do you find the GCF?
List the factors or prime factors for each number, identify the factors they share, and choose the largest shared factor.
Can the GCF be found for more than two numbers?
Yes. The same process works for two, three, or more whole numbers as long as you compare the factors that all numbers share.
What happens if one number is zero?
Zero can be included with non-zero numbers. The GCF is based on the non-zero values because every non-zero number divides zero evenly.
How can a GCF calculator help students?
Students can check factor lists, compare prime factorization, and see why the final answer is the largest shared divisor.