How many calories do you burn an hour playing tennis?

It depends on such things as your body weight, your degree of fitness, how hard you are playing, and whether you are playing on hard ground or grass.

For example, a 70 minute session of tennis could (for some people) burn approximately 500 calories if arms are swung in big motions, your feet are moved a lot, and you use backhand and forehand with force. Kate Hudson swears by it.