Counting how many substrings in a cell

Sometime you need to know how many substrings there are in a cell containing a string, where each substring is seperated by, say, a comma. Consider the string Peter,Paul,Mary - how would you count how many people are in the list?

Let's say your list is in B2.

=LEN(B2)-LEN(SUBSTITUTE(B2,",",""))+1


Simply counting the string before and after the removal of commas will tell you how many are in the list.