The GCF Calculator helps you find the Greatest Common Factor (also called the Greatest Common Divisor) of two or more whole numbers. It breaks down each number into its prime factors, shows the Euclidean algorithm step by step, and also calculates the Least Common Multiple. All computation stays on your device — your data never touches the internet.
What Is the Greatest Common Factor?
The Greatest Common Factor (GCF) of two or more numbers is the largest positive integer that divides each of them without leaving a remainder. For example, the GCF of 12 and 18 is 6, because 6 divides both 12 and 18, and no larger number does. The GCF is also called the Greatest Common Divisor (GCD) or Highest Common Factor (HCF).
The GCF is useful when simplifying fractions — you divide numerator and denominator by their GCF. When splitting items into equal groups, the GCF tells you the largest possible group size. It also plays a key role in cryptography, where it is used in the RSA encryption algorithm.
How to Use This Calculator
- 1Enter your numbers — Type at least two positive whole numbers in the text area. Separate them with commas, spaces, or new lines.
- 2See instant results — The calculator updates in real-time as you type. You get the GCF, LCM, factor lists, and prime factorization.
- 3Follow the steps — The step-by-step section shows the Euclidean algorithm and how the LCM is derived from the GCF.
- 4Copy or explore — Click any Copy button to grab individual values, or Copy All to get everything at once.
The Formula for Finding GCF
Why Does the GCF Matter?
Frequently Asked Questions
The Greatest Common Factor (GCF) is the largest positive integer that divides two or more numbers without a remainder. It is also called the GCD (Greatest Common Divisor) or HCF (Highest Common Factor).
The Euclidean algorithm repeatedly divides the larger number by the smaller one and replaces the larger with the remainder. This process repeats until the remainder is zero. The last non-zero remainder is the GCF.
GCF is the largest number that divides all given numbers. LCM is the smallest number that all given numbers divide into. They are related by: a × b = GCF(a,b) × LCM(a,b).
Yes, you can enter up to 10 numbers at once. The calculator finds the GCF of all of them together. Simply separate each number with a comma, space, or new line.
Yes, the GCF Calculator is completely free to use with no subscriptions, hidden fees, or limits. Use it as many times as you need.
Yes. The responsive design ensures a seamless experience no matter what device you use.
Absolutely. All calculations happen locally in your browser. Your numbers never leave your device and nothing is stored on our servers.
Yes, the calculator automatically computes and displays the LCM along with the GCF. Both results come with step-by-step explanations.
Prime factorization breaks a number into its smallest prime building blocks. For example, 12 = 2 × 2 × 3. The calculator shows this for every number you enter.
The calculator works with positive whole numbers only. For GCF calculations, the sign does not affect the result since GCF is always positive.
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