I weigh 250 pounds, and I'm a 5'9 female. I do 400 jumping jacks a day, at 50 jump intervals at a time. How many calories am I burning a day?

Great start, good for you for putting in some exercise! The amount of calories you are burning also has to do with how vigorously you are doing the exercise, but I would estimate you are burning around 100-150 calories. 

It is always good (and more fun!) to mix up your exercise, so you may want to think about adding some other types of exercises in as well!