That’s a good question and differs for everyone depending on height, weight, gender and age. We can compute the amount of calories needed based on your basal metabolic rate, your physical activity for the day, and the thermic effect of food.

1. The basal metabolic rate (BMR) is the number of calories needed for the body to function properly when at rest. This accounts for about 60-70% of the daily calories needed. The Harris-Benedict formula calculates BMR like this:

• For an adult male: 66 + (6.3 * body weight in pounds) + (12.9 * height in inches) – (6.8 * age in years).
• For an adult female: 655 + (4.3 * weight in pounds) + (4.7 * height in inches) – (4.7 * age in years). Don’t ask me why the first number is 655 but it is.

2. Your physical activity for the day consumes the next highest number of calories accounting for 20-30%. Figure it like this:

• Sedentary (slug like, on the couch all the time) = BMR * .2
• Light Activity Level (light exercise 1-3 days per week) = BMR * .375
• Moderate Activity Level (moderate exercise 3-5 days per week) = BMR * .55
• High Activity Level (hard exercise 6-7 days per week) = BMR * .725
• Extreme Activity Level (workout fanatic!) = BMR * .9

3. The thermic effect of food is the amount of energy your body uses in order to digest all the food that you eat. This accounts for about 10% of calories needed per day and is computed by adding together BMR and physical activity for the day and multiplying by 10 percent.

Now just add up the results from 1, 2, and 3 and you have the number of calories you need each day to maintain your CURRENT weight. To make it easy to calculate all of these numbers, use this Calories Needed Daily Calculator.