# LCM Calculator (Least Common Multiple)

URL: https://speedycalculator.com/calculators/math/lcm/
Last updated: 2026-10-25

> The LCM calculator finds the least common multiple of up to three whole numbers, the smallest number they all divide into. It is used for common denominators, scheduling and gear problems.

## Inputs

- First number
- Second number
- Third number (optional, 0 to skip)

## Results

- Least common multiple
- GCF of first two

## Formula

```
lcm(a, b) = |a × b| ÷ gcd(a, b)
```

## Explanation

The least common multiple is the first number that appears in every input’s list of multiples.

### How to use the LCM Calculator

- **First number**
- **Second number**
- **Third number (optional, 0 to skip)**

Results update as you type, and every field accepts the units shown in its menu.

### How it works

Divide the product of two numbers by their greatest common factor; repeat with the third number.

### Inputs explained

FieldWhat to enterFirst numberA numberSecond numberA numberThird number (optional, 0 to skip)A number

## Worked example

Inputs — First number: 4; Second number: 6; Third number (optional, 0 to skip): 10.

Results — **Least common multiple = 60**; GCF of first two = 2.

## Key terms

- **Multiple**: The product of a number and an integer.

## FAQ

**How is LCM used with fractions?**
The LCM of denominators is the least common denominator.

**Is LCM always at least the largest number?**
Yes.

**What formula does the LCM Calculator use?**
lcm(a, b) = |a × b| ÷ gcd(a, b).