Factorial Calculator (n!)

Factorial Calculator

Instead of calculating out a factorial 1 digit at a time, use this calculator to calculate the factorial, n! of a number n.  Enter an integer, up to 4 digits long, and choose if you want the full integer answer or abbreviated scientific notation. If you select the Full Integer Answer for large factorials, you may want to copy the result and paste it into another document to view it.

What is a factorial?

In mathematics, there are n! ways to arrange n objects in sequence. "The factorial n! gives the number of ways in which n objects can be permuted."[1] For example:

• 2 factorial is 2! = 2 x 1 = 2
  -- There are 2 different ways to arrange the numbers 1 through 2. {1,2,} and {2,1}.
• 4 factorial is 4! = 4 x 3 x 2 x 1 = 24
  -- There are 24 different ways to arrange the numbers 1 through 4. {1,2,3,4}, {2,1,3,4}, {2,3,1,4}, {2,3,4,1}, {1,3,2,4} ..... etc.
• 5 factorial is 5! = 5 x 4 x 3 x 2 x 1 = 120
• 0 factorial is a definition: 0! = 1.  There is exactly 1 way to arrange 0 objects.

References

[1] For more information on factorials please see http://mathworld.wolfram.com/Factorial.html