How Many Calories Are Needed Per Day?

Whether you want to lose, gain or maintain your weight, it all starts with simple math.

What is a Calorie

• A calorie is a unit of energy. Think of it as the "gasoline" that fuels your body. Instead of miles, calculate the number calories it takes to run your body for a 24-hour period.

The Formula

• The human body requires about 15 calories per pound per day to keep it running. A 100 pound person, for example, needs 100 x 15, or 1,500 calories, to maintain his or her weight.

To Lose a Pound

• Losing 1 pound requires burning 3,500 calories more than is required for "daily fuel." For example, if our 100 pound person reduced his calorie intake by 100 calories a day, it would take 35 days to lose a pound.

Gaining Weight

• The same formula applies for gaining weight. Consume 3,500 calories more than your body requires, and you will gain a pound.

The Activity Variable

• Activity level and metabolism have an impact on the calorie requirement. A more active person might be able to consume more calories without gaining weight. Conversely, a sedentary person might burn fewer than the average 15 calories per pound and have to reduce his calorie intake further or increase his activity to lose or maintain.