The calculations are estimates and should only be be used as guidelines. Your ideal weight will depend on your frame size (small, medium or large), muscle mass and fitness level. The calculation results will be innacurate for under 18's, the elderly, and athletic people.
Please note that your age and activity inputs will only affect your daily caloric needs for weight loss. The result given in calories would be your daily requirements in order to lose an average of 1 pound/week.