LCM Calculator

A fast, private, browser-based Least Common Multiple calculator with step-by-step solutions, multiple solving methods, and BigInt-safe calculations.

Overview

LCM Calculator helps students, teachers, and engineers find the least common multiple of two or more whole numbers instantly. It is designed to be simple, accurate, and educational: you get the final answer, the GCF/GCD, and the working behind the result.

All Calculators

• LCM Calculator — Find the least common multiple of two or more numbers with four methods and full steps.
• GCD / GCF Calculator — Find the greatest common divisor / greatest common factor with Euclidean-algorithm steps.
• Prime Factorization Calculator — Break any whole number into prime factors with an animated factor tree.
• Factors Calculator — List every factor, factor pair, count, and sum for a whole number.
• Prime Number Checker — Instantly test whether a number is prime or composite.
• Fraction Simplifier Calculator — Reduce any fraction to its lowest terms.

Features

• Four solving methods
  • Prime Factorization
  • GCF Formula: (a × b) ÷ GCF(a, b)
  • Listing Multiples
  • Division (Ladder) Method
• Step-by-step solutions for transparent, exam-ready working
• Works with 2 or more numbers
• BigInt-safe calculations for large values
• Private by design — calculations run in the browser
• No sign-up required
• Offline-friendly
• Keyboard accessible
• Responsive and dark-mode ready
• Up to 100 numbers supported

Common Use Cases

• Homework and exam practice
• Lowest common denominator problems
• Scheduling and timing problems
• Gear ratio and engineering calculations
• Prime factor learning and number theory drills

Example inputs

4, 6
12, 18, 24
3, 5, 7
8, 9, 21
15, 20, 25, 30

Calculation methods

Prime Factorization

Break each number into prime factors and take the highest power of every prime.

GCF Formula

Use the identity:

LCM(a, b) = (a × b) ÷ GCF(a, b)

Listing Multiples

List multiples until the first common value appears.

Division (Ladder)

Divide by common primes until no further division is possible, then multiply the divisors.

Why use this calculator?

• For homework and exam prep
• For teaching math concepts clearly
• For engineering and scheduling problems
• For finding the lowest common denominator when working with fractions

Privacy

All calculations happen in your browser. Nothing is uploaded.

License

MIT license-fully free

Contributing

Pull requests and improvements are welcome. Good contributions include:

• UI/UX enhancements
• New math tools
• Accessibility improvements
• Documentation fixes
• Test coverage