About the GCF calculator
This free GCF calculator finds the Greatest Common Factor (GCF) of two or more positive integers. The GCF is the largest positive integer that divides each of the numbers with no remainder. It is also called the Greatest Common Divisor (GCD). You enter the numbers separated by commas or spaces (e.g. 12, 18, 24), click Get result, and the tool shows GCF(numbers) = result. The calculator uses the Euclidean algorithm to compute the GCF efficiently. No sign-up is required; it is mobile-friendly and runs in your browser.
The GCF is used to simplify fractions (divide numerator and denominator by their GCF to get lowest terms), to find common factors in algebra, and to solve problems about divisibility and sharing. For example, GCF(12, 18) = 6, so 12/18 simplifies to 2/3. For more than two numbers, the GCF is computed by repeatedly taking the GCF of pairs: GCF(a, b, c) = GCF(GCF(a, b), c). This calculator handles any number of integers and shows the result clearly.
Use this GCF calculator for homework, simplifying fractions, or any time you need the greatest common factor of two or more numbers. Enter at least two positive whole numbers; non-integers and negative values are ignored. For the least common multiple (LCM) of two or more numbers, use an LCM calculator.
The GCF calculator is free, responsive on phones and tablets, and requires no account. It uses the Euclidean algorithm (repeated division: GCF(a, b) = GCF(b, a mod b) until the remainder is 0), which is fast even for large numbers. Pair it with the LCM calculator when you need both GCF and LCM for the same set of numbers.