The number of calories you need to maintain your present weight, according to your height and age, is also dependent on your activity level. Activity levels can range from sedentary to extremely active. Naturally, someone with a higher activity level would burn more calories during the day and need to replenish those calories to maintain his present weight. If you intend to lose weight, you will need to take in fewer calories per day and if you want to gain weight, you will need to take in more. There are 3500 calories in 1 lb.
The Harris-Benedict equation is a formula that takes your basal metabolic rate and multiplies it by an activity factor to figure your daily calorie intake to maintain your present weight. Basal metabolic rate is the rate your body consumes calories when at rest. The Harris-Benedict formula defines sedentary as having little or no exercise, lightly active as having light exercise or sports one to three times per week, moderately active as participating in moderate exercise or sports three to five times per week, very active as participating in hard sports six to seven times per week and extremely active as very hard exercise or sports plus a physical job or training twice a day.
Calories needed to maintain present weight for 25-year-old men are as follows: a man 5 feet 9 inches tall weighing 165 lbs. who is moderately active would need 2700 calories; the same size man who is sedentary would need 2250 calories. A 6-feet 2-inch man weighing 190 lbs. who is moderately active would need 3029 calories per day, while the same size man who is sedentary would need 2524 calories.
A 25-year-old 5-feet 2-inch woman weighing 120 lbs. who is moderately active would need 1994 calories to maintain present weight, while that same woman, if sedentary, would need 1661 calories. A 5-feet 7-inch woman weighing 150 lbs. who is sedentary would need 1851 calories, but if she is extremely active would need 2962 calories.
For 35 year-old men, the calories needed to maintain present weight are as follows: a 5-feet 7-inch man weighing 180 lbs. who is very active would need 3060 calories; a 5-feet 7-inch man weighing 180 lbs. who is sedentary would need 2250 calories per day. A 6-foot man weighing 220 lbs. who is very active would need 3590 calories, while that same size man who is sedentary would need 2640 calories.
A 5-feet 4-inch moderately-active woman would need 2067 calories per day, while an extremely-active woman of the same size would need 2756. A 5-feet 10-inch woman weighing 160 lbs. who is sedentary would require 1864 calories per day but if she were very active would need 2535 calories.
A 45 year-old man who is 5 feet 10 inches tall and weighs 175 lbs. would need 2261 calories if lightly active; the same size man who is extremely active would require 3478 calories. A 6-feet 3-inch man weighing 225 lbs. who is sedentary would need 2643 calories but if very active, would need 3594 calories.
A 45-year-old woman who is 5 feet tall, weighs 110 lbs. and is moderately active would use 1775 calories per day. If this same woman were extremely active, she would require 2366 calories. A 5-feet 8-inch sedentary woman weighing 155 lbs. would need 1766 calories nand if she were lightly active would need 1837 calories.