I need to know how many calories one would burn if they just sat at a desk all the time on their 9-5.
To calculate the amount of calories you burn on a daily basis you can add your BMR and activity calorie expenditure.
Basal Metabolic Rate (BMR) is the amount of energy your body requires at rest just to maintain your bodily functions. The BMR is expressed in calories. You can roughly calculate your BMR with an online BMR calculator using your gender, weight, height and age.
Activity Calorie Expenditure - Next you can use the calorie activity calculator, entering your weight and the number of minutes "studying" to determine the additional calories you spend while sitting at your desk.
For example, a 35 y.o., 5' 7" man weighing 150#, would have a BMR of 1597 to 1611.0 calories depending on the calculator used. Desk work for 8 hrs (or 480 minutes) adds ~ 1,008 calories for a total of 2619 calories per day (if my math is right). For metric values, here is a metric BMR calculator.
Realize that these calculators are approximations and do not take into account your body fat percentage.
A calculator can be useful in figuring this out. Visit this link: http://www.healthstatus.com/calculate/cbc to calculate calorie burn based on your weight.