Combinatorics
_{n}P_{k}  =  n!
(n  k)!

Calculator (fill both fields and click 'Calculate'):
Total number of items:n =
How many to choose:k =
Number of permutations:
In scientific notation:
P_{k}(n)  =  n^{k} 
Calculator (fill both fields and click 'Calculate'):
Total number of items:n =
How many to choose:k =
Number of permutations:
In scientific notation:
_{n}C_{k}  =  n!
k!(n  k)!

=  (  n
k

) 
Calculator (fill both fields and click 'Calculate'):
Total number of items:n =
How many to choose:k =
Number of combinations:
In scientific notation:
C_{r}(n, k)  =  (k + n  1)!
k!(n  1)!

Calculator (fill both fields and click 'Calculate'):
Total number of items:n =
How many to choose:k =
Number of combinations:
In scientific notation:
Combinatorics calculator is a free online tool for calculations of numbers of combinations and permutations.