LCM Calculator

How to use the LCM calculator

1. Enter 2–20 positive whole numbers, separated by spaces, commas, semicolons or newlines. Each entry can have up to 12 digits.
2. Do not put grouping separators inside a number. For example, type 1200; 1800, not 1,200; 1,800. A comma separates entries; it is not a decimal mark.
3. Read the exact LCM. Open Calculation details for the overall GCD and the pairwise steps, or copy the result with its input list.

What the least common multiple means

The LCM is the smallest positive whole number divisible by every entered number with no remainder. Lowest common multiple and least common multiple mean the same thing.

For two positive integers, LCM(a, b) = (a ÷ GCD(a, b)) × b. For more numbers, combine the first two, then combine their LCM with the next number until every entry is included.

The GCD, also called the greatest common factor, is the largest positive integer that divides every entry. It is not the LCM. For 12 and 18, the GCD is 6 and the LCM is 36.

Worked examples

For 12 and 18, the GCD is 6. Their LCM is (12 ÷ 6) × 18 = 36. It is smaller than the product 216 because the numbers share factors.

For 12, 18 and 30, first find LCM(12, 18) = 36, then LCM(36, 30) = 180. The overall GCD of the three original numbers is 6.

For fraction denominators 8 and 12, the least common denominator is their LCM, 24. That does not add the fractions or change their numerators; use the separate Fraction Calculator for fraction arithmetic.

Positive integer input and exact output

This version accepts 2–20 positive integers with at most 12 entered digits each, including leading zeros. Zero, negative numbers, decimal values, fractions and expressions are not supported.

Results remain exact, including integers too large for ordinary floating-point arithmetic. Long answers wrap without removing digits. The page does not generate prime factorizations, schedules or lists of multiples.

Your entries

The calculation runs in your browser. This tool adds no input upload, saved record or input-bearing URL. Existing website consent, analytics and network services remain separate.