Try...

C1, copied down:

=COUNTIF($B$1:B1,B1)

Hope this helps!

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In article ,
style0 wrote:

I am out of ideas. I need to count how many times a category is repeated.
Here's what I have:
name category
1 a aa
2 b aa
3 c aa
4 d bb
5 e aa
6 f aa
7 g bb
8 h cc
9 i cc
10 j aa

Here's what I need:
name category count
1 a aa 1
2 b aa 2
3 c aa 3
4 d bb 1
5 e aa 4
6 f aa 5
7 g bb 2
8 h cc 1
9 i cc 2
10 j aa 6

Same thing sorted (if it helps):
name category count
1 a aa 1
2 b aa 2
3 c aa 3
4 e aa 4
5 f aa 5
6 j aa 6
7 d bb 1
8 g bb 2
9 h cc 1
10 i cc 2

Thank you in advance.