# 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.

Factorial Calculator (n!)

## 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