Trouble working out how many cals burned during classes.

I've recently started going to classes held at my gym the classes are called "tummy Hips & Thighs" so you can imagine the areas its designed to target, Im having trouble figuring out how to track these classes though, because I know im burning calories doing them but I dont know how many. the classes consist of roughly 10 mins of various squats - 15 mins of crunches and pushups, leg raises stuff like that - 10 mins of various sort of cardio like star jumps, jogging, and like side stepping travel stepping stuff like that.
These classes really leave me feeling drained like i've put in a lot of effort, im not sure if its because the class is really good or if its just because im so unfit.

How would you guys go about tracking a session like this?