try using myfitnesspal.com (if you have a smart phone or ipod the app is great)

You can put in your expenditures (exercise) and your intake and see if they match. I've been using it for a month or two and I think that it is relatively accurate. I've been keeping my intake to around 100-150 calories less/day than my expenditures (base + exercise) and I've been slowly losing a few pounds.