Do you keep close track of how much formula your infant drinks?

I breast feed my son, only because he will not latch on. Doing this, I am able to know exactly what he is getting and when. I do not keep a chart of it... But it helps me knowing that he is getting how much he needs - no worry of over feeding or under feeding. I guess it's just nice to know... but when I formula fed him at first I really didn't pay attention - I just fed him till he no longer wanted anymore