LCM & GCF Calculator

LCM & GCF Calculator finds the greatest common factor (also called GCD or HCF) and the least common multiple of two or more whole numbers. It shows the prime factorisation of every number, the prime powers used for each answer and a check with Euclid’s algorithm, all calculated exactly.

GCF and LCM come up when simplifying fractions, adding fractions with different denominators, scheduling repeating events and splitting items into equal groups. Seeing the factorisation and the steps makes the answer easy to check and to learn from.

1. Type or paste two or more integers, separated by commas, spaces, tabs or new lines.
2. Press Calculate LCM & GCF (or Ctrl/Cmd + Enter in the box).
3. Read the GCF and LCM, and their prime-power forms.
4. Review the prime factorisation of each number and the calculation steps.
5. Copy the summary or download it as a text file.

• GCF (GCD) and LCM for 2 to 50 integers
• Prime factorisation of every number with exponents
• Prime-power working for both answers, plus a Euclid’s algorithm check
• Negative numbers handled through absolute values, with an explanation
• Exact arbitrary-precision results — very large LCMs are never rounded
• Clear messages for zero, decimals, malformed values and too many digits

• Use the GCF to simplify a fraction: divide the numerator and denominator by it.
• Use the LCM as the common denominator when adding or subtracting fractions.
• A GCF of 1 means the numbers are coprime; their LCM is then their product.
• Remove zeros before calculating — every number divides 0, so it has no factorisation.