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# A to Z of Excel Functions: the COMBIN Function

1 September 2017

Welcome back to our regular A to Z of Excel Functions blog.  Today we look at the COMBIN function.

The COMBIN function

Are you often COMBIN the Excel functions to see how many subsets you can make?  This function returns the number of combinations for a given number of items (i.e. the number of distinct subsets of items where order is unimportant).  You should use COMBIN to determine the total possible number of groups for a given number of items.

The COMBIN function employs the following syntax to operate:

COMBIN(number, number_chosen)

The COMBIN function has the following arguments:

• number: this is required and represents the number of items
• number_chosen: this is also required.  This denotes the number of items in each combination.

It should be further noted that:

• numeric arguments are truncated to integers
• if either argument is nonnumeric, COMBIN returns the #VALUE! error value
• if number < 0, number_chosen < 0, or number < number_chosen, COMBIN returns the #NUM! error value
• a combination is any set or subset of items, regardless of their internal order.  Combinations are distinct from permutations, for which the internal order is significant
• the number of combinations is as follows, where number = n and number_chosen = k:

where:

and n! denotes n x (n-1) x … x 2 x 1.