Calories Burned For a Planet Fitness Abs Class Work Out

I am going to start taking an abs class at my local Planet Fitness and I was wondering if anyone knew what my average calories burned might be. It doesn't have to be a perfect estimate but a ball park would do. Or do you know how I could go about finding out the average calories burned myself?

I don't have a heart rate monitor (unfortunately) and cant buy one at the moment so I was hoping someone on here might have some advice. Thanks!