Math & Algebra Tool

HCF / GCD Calculator

Find the Greatest Common Divisor (also known as HCF) of multiple numbers.

Separate values with commas or spaces.

Σ The Formula

GCF using Euclidean algorithm: GCF(a,b) = GCF(b, a mod b)

Real World Examples

Simple GCF
GCF(48, 18) = 6
Three Numbers
GCF(12, 18, 30) = 6
Simplify Fraction
48/18: GCF=6, simplified = 8/3
Tile Problem
Room 24×36 ft, largest square tile: GCF(24,36) = 12 ft

# About This Calculator

The Greatest Common Divisor (GCD), also known as the Highest Common Factor (HCF) or Greatest Common Factor (GCF), is the largest positive integer that divides each of the given integers without leaving a remainder. It's a fundamental concept in number theory with practical applications.

GCF is essential for simplifying fractions (divide numerator and denominator by their GCF), solving problems involving equal grouping or distribution, finding the largest square tiles that fit a rectangular space, and understanding number relationships. It's also crucial in cryptography and computer science algorithms.

The Euclidean algorithm efficiently finds GCF: GCF(a,b) = GCF(b, a mod b), repeating until remainder is 0. For multiple numbers, find GCF pairwise. Alternatively, list all factors and find the largest common one, or use prime factorization (multiply common prime factors with lowest powers).

This calculator handles multiple numbers simultaneously, shows step-by-step factor listings, and identifies all common factors. Perfect for homework, fraction simplification, or any problem requiring the largest common divisor.

How To Use

  1. Enter numbers separated by commas or spaces (e.g., "12, 18, 30").
  2. Click Calculate GCF.
  3. The tool will show you the common factors and the greatest one.

Frequently Asked Questions

Is GCD the same as HCF?+

Yes, Greatest Common Divisor (GCD), Highest Common Factor (HCF), and Greatest Common Factor (GCF) all refer to the same concept - the largest number that divides all given numbers evenly.

How do I use GCF to simplify fractions?+

Find the GCF of numerator and denominator, then divide both by it. For 48/18: GCF(48,18)=6, so 48÷6 / 18÷6 = 8/3. This gives the simplest form. If GCF=1, the fraction is already simplified.

What's the GCF of two prime numbers?+

Always 1! Prime numbers have no common factors except 1. For example, GCF(7,11)=1, GCF(13,17)=1. This is why fractions with prime denominators often can't be simplified.

Can GCF be larger than one of the numbers?+

No, the GCF can never exceed the smallest number in the set. In fact, if one number divides all others, it IS the GCF. For example, GCF(12, 24, 36) = 12 because 12 divides all three.

How is GCF related to LCM?+

They're inversely related! For two numbers a and b: GCF(a,b) × LCM(a,b) = a × b. If you know one, you can find the other. For example, GCF(12,18)=6 and LCM(12,18)=36, and 6×36=12×18=216.

Can GCF be 1?+

Yes, if the numbers share no common factors other than 1, they are called 'coprime' or 'relatively prime'.

About

The Greatest Common Divisor (GCD), also known as the Highest Common Factor (HCF) or Greatest Common Factor (GCF), is the largest positive integer that divides each of the given integers without leaving a remainder. It's a fundamental concept in number theory with practical applications.

GCF is essential for simplifying fractions (divide numerator and denominator by their GCF), solving problems involving equal grouping or distribution, finding the largest square tiles that fit a rectangular space, and understanding number relationships. It's also crucial in cryptography and computer science algorithms.

The Euclidean algorithm efficiently finds GCF: GCF(a,b) = GCF(b, a mod b), repeating until remainder is 0. For multiple numbers, find GCF pairwise. Alternatively, list all factors and find the largest common one, or use prime factorization (multiply common prime factors with lowest powers).

This calculator handles multiple numbers simultaneously, shows step-by-step factor listings, and identifies all common factors. Perfect for homework, fraction simplification, or any problem requiring the largest common divisor.

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