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GCF Calculator – Find the Greatest Common Factor Online


Quickly calculate the Greatest Common Factor (GCF) of two or more numbers. Simplify fractions, reduce ratios, and solve math problems instantly with our GCF Calculator.

Need to simplify fractions, reduce ratios, or solve math problems quickly? Our GCF Calculator instantly finds the Greatest Common Factor of any two or more numbers, saving you time and ensuring accuracy.

Enter two or more numbers below to instantly find their Greatest Common Factor (GCF). Separate numbers with commas if you want to calculate for multiple values.

Tip: Use commas to enter multiple numbers (e.g., 12, 18, 24). Our calculator will return the largest factor that divides all of them evenly.

What is a GCF Calculator?

The GCF Calculator is a simple yet powerful tool that determines the Greatest Common Factor (GCF), also called the Highest Common Factor (HCF) or Greatest Common Divisor (GCD). The GCF is the largest number that divides two or more integers evenly. With this calculator, you can instantly simplify fractions, reduce ratios, and solve everyday math problems.

How the GCF Calculator Works

Behind the scenes, the calculator uses efficient algorithms to find the GCF of numbers you enter. It may apply prime factorization, the Euclidean algorithm, or direct factor comparison to deliver the correct result in seconds. Whether you input two numbers or several, the tool quickly computes the largest factor they all share.

Listing Factors

This method lists all factors of each number and selects the largest one in common. Example: factors of 12 are {1, 2, 3, 4, 6, 12}; factors of 18 are {1, 2, 3, 6, 9, 18}. The GCF is 6.

Prime Factorization

Each number is broken down into prime numbers. The product of common prime factors is the GCF. Example: 12 = 2 × 2 × 3, and 18 = 2 × 3 × 3. Common factors = 2 × 3 = 6.

Euclidean Algorithm

The calculator also applies division repeatedly: divide the larger number by the smaller and continue with remainders until you reach zero. The last nonzero divisor is the GCF.

How to Use the GCF Calculator

  1. Enter two or more integers into the calculator fields.
  2. Press “Calculate” to run the computation.
  3. View the GCF instantly, along with optional steps for learning.
  4. Use the result to simplify fractions, ratios, or algebraic problems.

What the GCF Tells You

  • Simplify fractions: Divide numerator and denominator by the GCF.
  • Reduce ratios: Convert 60:90 into 2:3 using the GCF of 30.
  • Factor expressions: Pull out the GCF when factoring algebraic terms like 12x² + 18x ? 6x(2x + 3).
  • Divide evenly: Use GCF to split items into equal groups with no remainder.

Real-Life Examples of GCF

  • Example 1: GCF of 14 and 28 = 14.
  • Example 2: GCF of 45 and 75 = 15 (useful for simplifying 45/75 to 3/5).
  • Example 3: GCF of 8, 12, and 20 = 4.

GCF vs LCM: Know the Difference

The GCF and LCM are related but different:

  • GCF (Greatest Common Factor): the largest factor dividing all numbers.
  • LCM (Least Common Multiple): the smallest multiple all numbers share.

Example: For 12 and 18, GCF = 6 and LCM = 36. Many calculators, including ours, provide both results.

Why Use Our GCF Calculator?

  • Fast: Instant results for any numbers.
  • Accurate: No errors, even with large inputs.
  • Educational: Step-by-step breakdowns for learning.
  • Versatile: Works for two numbers or multiple values at once.

Use the GCF Calculator to simplify your math, whether in school, teaching, or solving real-world problems. It’s quick, reliable, and designed to make calculations easy for everyone.


Frequently Asked Questions

What is the GCF Calculator used for?

The GCF Calculator helps you quickly find the Greatest Common Factor of two or more numbers, useful for simplifying fractions, reducing ratios, and solving math problems.

How do I calculate the GCF of two numbers?

You can use the Euclidean algorithm, prime factorization, or simply enter the numbers into the GCF Calculator for instant results.

Is GCF the same as HCF or GCD?

Yes, GCF (Greatest Common Factor), HCF (Highest Common Factor), and GCD (Greatest Common Divisor) are different names for the same concept.

Can the GCF be larger than the smallest number?

No. The GCF is always less than or equal to the smallest number in the set.

What happens if the GCF is 1?

If the GCF is 1, the numbers are called relatively prime or coprime, meaning they share no common factors other than 1.


Brian Mbiki of c4calc

Brian Mbiki

A Mathematician, Software and Web Development autodidact.

Brian Mbiki writes on Math, Software and web development and has keen interest in Cryptocurrency investments and Blockchain Technology.