# 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

Factorial Calculator (n!)

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

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