# Factorial Calculator

You can use our Factorial Calculator to calculate the factorial of any real number between 0 and 5,000.

To use this calculator just enter a positive integer number less than or equal to 5000. After you click "Calculate Factorial" the result will be displayed in the output box.

## Reference

The factorial of n, or n! is the product of all positive integer numbers from 1 to n.

The value n! is called "n factorial" and is calculated by following formula:

**
n! = n × (n - 1) × (n - 2) × . . . × 1
**
, n > 0

By convention, 0! = 1

For example, the factorial of 7 is equal to 7×6×5×4×3×2×1 = 5040.

### Stirling's Approximation

n! ≈ √
2π × n
× n
^{
n
}
×
*
e
*
^{
-n
}

Example:
6! ≈ √
2π × 6
× 6
^{
6
}
×
*
e
*
^{
-6
}
≈ √
37.6991
× 46656 × 0.002478 ≈ 709.862

### Table of Factorials from 1! to 15!

Number (n) | Factorial (n!) |
---|---|

0 |
1 |

1 |
1 |

2 |
2 |

3 |
6 |

4 |
24 |

5 |
120 |

6 |
720 |

7 |
5040 |

8 |
40320 |

9 |
362880 |

10 |
3628800 |

11 |
39916800 |

12 |
479001600 |

13 |
6227020800 |

14 |
87178291200 |

15 |
1307674368000 |

You may also be interested in our Summation Calculator