You don't have to count the teeth, if you look closely there's a number stamped on each ring. That number tells how many teeth the ring has. It's hard to find but its there, good excuse for cleaning your cassette!

On your crankset there is a number on each ring, for example, mine has 48-110 stamped on the big ring and 34-110 on the small ring. That means my front chainrings are 48-34. I have a compact double that's why the 2 smaller rings on the front.