Four proven methods, full steps
Switch between Prime Factorization, the GCF formula, Listing Multiples, and the Division (ladder) method. Each shows transparent, exam-ready working — perfect for learning, not just answers.
⚡ 2026 Edition · Free Forever
Least Common Multiple Calculator with step-by-step solutions
Find the LCM of two or more numbers instantly. Pick your preferred method — prime factorization, the GCF formula, listing multiples, or the division ladder — and see every step of the working, plus the GCF/GCD.
No sign-up
Works offline
Up to 100 numbers
Private — runs in your browser
LCM Calculator
Live · BigInt-safe
Quick answer
What is the Least Common Multiple?
The Least Common Multiple (LCM) of two or more whole numbers is the smallest positive number that every input divides into evenly. For example, the LCM of 4 and 6 is 12, because 12 is the first number that appears in both the 4-times table (4, 8, 12, …) and the 6-times table (6, 12, …). The quickest formula is LCM(a, b) = (a × b) ÷ GCF(a, b).
Why this tool
A complete LCM calculator, not just an answer box
Built for students, teachers and engineers who need verified results and clear working.
Unlimited & big numbers
Powered by BigInt — compute the LCM of dozens of values or very large integers without precision loss.
GCF / GCD included
Every result also reports the Greatest Common Factor and the product of inputs, so you see the full relationship.
Lowest common denominator
The LCM of denominators is the LCD — use this as a fraction common-denominator tool too.
Fast, private & accessible
Calculations run entirely in your browser — nothing is uploaded. The interface is keyboard-navigable, screen-reader friendly, dark-mode ready, and responsive on every device.
How it works
Get the LCM in three steps
1
Enter your numbers
Type two or more whole numbers separated by commas or spaces, e.g. 12, 18, 24. Use a quick-example chip to try it instantly.
2
Choose a method
Select prime factorization, the GCF formula, listing multiples, or the division ladder — whichever your class or task requires.
3
Read the worked solution
Get the LCM, the GCF/GCD, and a clear step-by-step explanation you can copy or learn from.
Worked examples
Common LCM results at a glance
Tap any row to load it into the calculator and see the full working.
More patterns and tables are available on the LCM guide.
FAQ
Frequently asked questions
How do you find the LCM of two numbers?
The fastest method is the GCF formula: LCM(a, b) = (a × b) ÷ GCF(a, b). For 12 and 18, GCF = 6, so LCM = (12 × 18) ÷ 6 = 36. You can also use prime factorization or list multiples — this calculator shows all four approaches.
What is the difference between LCM and GCF?
The LCM is the smallest number that every input divides into; the GCF is the largest number that divides every input. They are connected by the identity LCM(a,b) × GCF(a,b) = a × b.
Can it calculate the LCM of three or more numbers?
Yes. Enter any list, such as 6, 8, 12, 15, and the calculator finds the LCM of the whole set by combining numbers pairwise.
Is the LCM the same as the lowest common denominator?
For adding or comparing fractions, the lowest common denominator (LCD) is exactly the LCM of the denominators — so this tool works as an LCD calculator too.
Math toolkit
More free calculators
Every tool includes step-by-step working, a visual diagram and AI insights.
GCD / GCF Calculator
Greatest common divisor & HCF.
Open toolPrime Factorization
Break a number into prime factors.
Open toolFactors Calculator
List every divisor & factor pair.
Open toolPrime Number Checker
Is a number prime or composite?.
Open toolFraction Simplifier
Reduce fractions to lowest terms.
Open toolSolve any LCM problem in seconds
From homework and exam prep to scheduling and engineering timing, get accurate least common multiples with clear working — free, private, and on any device.
Open the calculator