Greatest common factor (GCF) worksheets
Find the biggest number that divides evenly into every number in the problem — also called the greatest common divisor (GCD) or highest common factor (HCF).
How to solve them
- List the factors of each number: 18 → 1, 2, 3, 6, 9, 18 and 24 → 1, 2, 3, 4, 6, 8, 12, 24.
- Circle the factors they share: 1, 2, 3, 6.
- The biggest shared factor is the GCF (6).
Ready-to-print greatest common factor (gcf) worksheets
Nine fixed sets — three per level. Each PDF has the problems followed by the answer key.
Levels
| Level | Problems | Grade |
|---|---|---|
| Easy | Two numbers up to 36 | 4–5 |
| Medium | Two numbers up to 100 | 6 |
| Hard | Three numbers up to 150 | 6 |
Why the GCF matters
Dividing the numerator and denominator of a fraction by their GCF simplifies it in one step: 18/24 → divide by 6 → 3/4. The GCF is also used to factor expressions in algebra, such as 6x + 9 = 3(2x + 3).
Charts that help
- Multiplication chart 1–12 — free printable PDF
More math generators: multiplication, long division, comparing fractions, multiplying fractions, adding fractions, least common multiple (lcm), area, place value, addition, subtraction, combining like terms. Or print a whole grade: 4th, 5th and 6th grade math.
Frequently asked questions
Can the GCF be 1?
Yes — numbers like 8 and 15 share no factor except 1, so their GCF is 1. Most problems on these sheets have a bigger common factor.
Is GCF the same as GCD and HCF?
Yes. Greatest common factor, greatest common divisor and highest common factor are three names for the same thing.
Is there an answer key?
Yes. The PDF always ends with an answer key for the same problems, so you can print the questions for students and keep the key. Every answer is checked by automated tests.
Can I print the same worksheet again later?
Yes. Every sheet has a set number (the seed) printed in the footer and saved in the page address. Open the same link, or type the same level, count and set number, and you get exactly the same problems and answer key.