A2: a date of birth

B2:

=(DATEDIF(A2,TODAY(),"Y")=3)+0

Then:

=SUM(B2:B100)

Or:

=SUMPRODUCT((DATEDIF($A@:$A$100,TODAY(),"Y")=3)+0 )

Sue wrote:
How do I get excel to work out how old someone is in years as at todays date
on any given day, when I enter a date of birth into a specific column on
excel 2003. I then need the formula to recognise if it is over 3 years of
age and irrelevant of how many years past 3, that it will put a one in the
formula cell column for that row. All the 1's in that column are
subsequently summed to give me a total of all people over 3 years of age.
Currently I am entering the date of birth and then manually calculate their
age and put the 1 into the column which then gets summed.
Any ideas?