I think this calculator is useful. It shows you how many calories you need to maintain, or fat loss, and or extreme fat loss. and it explains which one is right for you.
Calculator:
http://www.freedieting.com/tools/calorie_calculator.htm
(and if you look the right menu, there are some other calculators there as well for: Ideal Weight .... bmi .... Nutrient Ratios... etc)
I hope this is useful to some of you