LCM Calculator
LCM Calculator: free, instant and private. Euclid's algorithm is over two thousand years old and still the fastest way: keep replacing the larger number with the remainder until it hits zero.
How the LCM Calculator works
The LCM Calculator takes Numbers (separated by spaces, commas or lines) and returns the answer instantly — no button to hunt for, no page reload. Euclid's algorithm is over two thousand years old and still the fastest way: keep replacing the larger number with the remainder until it hits zero. HCF answers "what shared step size exists", LCM answers "when do the cycles realign" — gears, bus timetables, repeating decimals.
Enter your own numbers to replace the example values; the result panel updates as you type. Everything runs in this single page, so nothing you enter leaves your device.
Formula used
HCF via Euclid: gcd(a, b) = gcd(b, a mod b); LCM = a × b ÷ gcd(a, b)
| Symbol | Meaning |
|---|---|
| HCF / GCD | the largest number that divides every input |
| LCM | the smallest number every input divides |
Euclid's algorithm is over two thousand years old and still the fastest way: keep replacing the larger number with the remainder until it hits zero. HCF answers "what shared step size exists", LCM answers "when do the cycles realign" — gears, bus timetables, repeating decimals.
Inputs used: Numbers (separated by spaces, commas or lines).
Worked example
Take the default example — numbers (separated by spaces, commas or lines) of 12, 18, 30:
- count: 3
- gcd: 6
- lcm: 180
- hcf: 6
Frequently asked questions
- What formula does the LCM Calculator use?
- It uses HCF via Euclid: gcd(a, b) = gcd(b, a mod b); LCM = a × b ÷ gcd(a, b), where HCF / GCD is the the largest number that divides every input; LCM is the the smallest number every input divides.
- Is the LCM Calculator free?
- Yes. There is no signup, no usage limit and no watermark — the checker runs entirely in your browser.
- How do I read the result?
- Euclid's algorithm is over two thousand years old and still the fastest way: keep replacing the larger number with the remainder until it hits zero. HCF answers "what shared step size exists", LCM answers "when do the cycles realign" — gears, bus timetables, repeating decimals.
- Does the LCM Calculator store or send my data?
- No. Every calculation happens locally in the page, so the numbers you type are never uploaded or logged.
- Does it work on a phone and offline?
- Yes — the page is a single lightweight file that adapts to any screen size. Once it has loaded it keeps working without a network connection.