After seeing this list, lack of time is no reason not to exercise. See how many calories you can burn by exercising for 15 minutes.
Next time during the lunch break, grab your skipping rope or get on the cross trainer in the evening when you haven't had time to go to the gym. According to this list from the Fitsugar website, it really makes sense.
The number of calories is based on a body weight of 60 kilos.