GCF & LCM Calculator

The greatest common factor (GCF, also called the greatest common divisor or HCF) is the largest whole number that divides every number in a list; the least common multiple (LCM) is the smallest positive number that every one of them divides. This calculator computes both for 2 to 10 whole numbers at once — paste them separated by spaces, commas or line breaks and run it.

The GCF is found with the Euclidean algorithm, and every division is written out: for 48 and 180 you see 180 = 3 × 48 + 36, then 48 = 1 × 36 + 12, then 36 = 3 × 12 + 0, so the GCF is 12. The LCM is then derived through the identity lcm(a, b) = a × b ÷ gcd(a, b) — for the same pair that is 48 × 180 ÷ 12 = 720. All arithmetic uses exact big integers, so even the LCM of ten 12-digit numbers is computed without overflow.

Each input number is also decomposed into its prime factorization in exponent form — 48 = 2⁴ × 3, 180 = 2² × 3² × 5 — which is the textbook way to see why the GCF collects the shared prime powers while the LCM collects the highest ones. That makes the tool a natural companion for reducing fractions, finding common denominators, aligning repeating schedules and solving divisibility problems.

Everything runs locally in your browser: no sign-up, no server round-trips, and the full working can be copied as plain text for homework or documentation with one click.