In terms of calorie burning, moderate jumping is about equal to running a 10-minute mile, although calorie burning is always a function of time, speed and fitness level.  Jumping is strenuous and so people typically jump in 10-minute sessions once or twice a day.  To start, jump in 1 to 3-minute rounds, alternating between fast and slow skipping with a 20 to 60 second rest in between, and then gradually build up to skipping faster during the rounds and decreasing the rest time in between. Read about jump rope workouts at About.com.