The goal is to create a deficit. In perfect science every 3500 calorie deficit means 1lb lost, this usually takes a person 3.5 days to create. However you dont have to workout to burn more than 1500 calories. You burn calories just by living. What you burn if you just lied in bed all day is called your BMR or Basal Metabolic Rate.
This site
http://www.freedieting.com/tools/calorie_calculator.htm will help give you an idea of how many calories you need, based on your physical activity level, height, weight , age, gender.
This site will