I am not sure if this is the one or similar to what you found but this one seems pretty accurate ( at least for me).
http://www.my-weight-loss-advisor.co...bohydrate.html
While you are there be sure to click on:
"There is some very important information about protein, fat and carbohydrate and overeating that you should know. "
and read that page... it sounds corny, but the calculation tips are great!
Hope it helps!