Prob a silly Q

I wear a heart rate monitor while i do the 30 day shred and surprisingly don't burn as many calories as I expected. I am 110 pounds and burn anywhere from 90-130 calories on level one and 150-160 calories doing level two. The more you weigh the more calories you burn (as long as you're really trying!) is a general rule of thumb. But maybe search 'circuit training' in the database and use that, it seems to be fairly similar with the calorie burn.