A formula for the number of possible combinations of r objects from a set of n objects. The above calculator does not allow repeated objects, that is each object can only be used once per set. It should also be noted that because the equation for determining combinations uses factorials, only small numbers can be used in this calculator.

# Notation and Units

## Combination vs. Permutation

To distinguish between combinations and permutations one must remember that if the order doesn't matter, it is a combination and if the order does matter, it is a Permutation.

# Notation

- n = The total number of objects under consideration
- r = The number of objects in the set under consideration
- C(n,r) = The total number of possible combinations