myfitnesspal and other online calculators?

Ow3593

Hi i have been using myfitnesspal since June but not been using my fitness pal for very long. I started using it around July 2nd. Before finding out about myfitnesspal i used to use other online calculators with the basal metabolic rate and the and daily activity added together. Almost all of these online calculators use the same method. These calculators would boost the amount of calories needed in a day if you did 1-3 exercises a week. I'm wondering if those were over estimations and how those other calculators determine the calories you need when it boosts your daily calorie needs even on the days you are not exercising. These two differences between myfitnesspal and other online calculators have me wondering why they do that and if it is accurate.

example: http://www.freedieting.com/tools/calorie_calculator.htm
webmd which is a trusted health website.