If you go through the entire day just sitting, doing no exercise, you still burn calories. To calculate how much, follow these steps:
1. Multiply your weight by 10 - this is how many calories your body needs for basic metabolic processes.
2. Factor in your activity level:
Sedentary: 20% (Sitting most of the day)
Lightly Active: 37.5% (Walking here and there; daily chores)
Moderately Active: 40% (Constantly moving around; daily exercise)
Very Active: 50% (Heavy exercise for prolonged periods of time, such as training for a sport)
Take the answer to #1 and take the corresponding percentage - this is how many calories you need to go about a typical day.
3. Figure the energy used in digestion: #1 + #2 * .1
4. Add #1, #2, and #3 together. This is how many calories you burn in a day.