Greatest common factor worksheets
Finding the greatest common factor (GCF) of two numbers, the largest number that divides into both. The GCF is how fractions get simplified in one step.
Download the free greatest common factor worksheet (PDF)
Greatest common factor worksheet
Mixed GCF and LCM practice
What’s on the worksheet
- 50 questions on greatest common factor, sized for US Letter paper
- 2 pages of questions plus an answer key on the last page
- Written for grade 6, matching Common Core 6.NS.B.4
- Name and date lines at the top, and room to show the work
Sample questions from this worksheet
- GCF of 8 and 16 =
- GCF of 18 and 99 =
- GCF of 30 and 15 =
- GCF of 42 and 24 =
- GCF of 50 and 30 =
- GCF of 32 and 64 =
Preview the worksheet and answer key
Make a new greatest common factor worksheet
Need another page for extra practice, a retake or a second group in class? The free Mathify Kids test maker builds a fresh greatest common factor worksheet with different numbers every time. Choose Core, Standard or Challenge level, print it with its own answer key, or let your child take it on screen and see the score straight away.
Greatest common factor: a worked example (GCF of 24 and 36)
- Factors of 24: 1, 2, 3, 4, 6, 8, 12, 24.
- Factors of 36: 1, 2, 3, 4, 6, 9, 12, 18, 36.
- The largest one in both lists is 12.
How to use it at home and in class
At home
Once the listing method is easy, show the prime factor method for bigger numbers. Ten problems a day works better than a whole sheet at once. Mark them together with the answer key, then ask your child to explain one they got wrong: finding the mistake themselves is where the learning happens.
In class
Use the first row as a warm-up, a full page for independent practice, or five questions as an exit ticket. For a retake or a second group, make a new version with the test maker so every child gets different numbers.
Mistakes to watch for
- Choosing a common factor that isn’t the greatest one, like 6.
- Confusing GCF with LCM.
What to practice before and after greatest common factor
- Before: prime numbers. If this sheet is a struggle, go back a step.
- After: least common multiple, once this one is mostly right.
- Learn it first: the greatest common factor lesson and the factors and multiples chart.
More factors & multiples worksheets
Last reviewed
Questions parents ask
What is the GCF used for?
Simplifying fractions in one step and splitting things into the largest equal groups, like packing 24 pencils and 36 erasers into matching kits.
What grade is this greatest common factor worksheet for?
It is written for grade 6 and matches Common Core standard 6.NS.B.4.
Can I get a different version of this greatest common factor worksheet?
Yes. Use the free Mathify Kids test maker to make a new greatest common factor worksheet with different numbers every time, at Core, Standard or Challenge level, with its own answer key.