Does anyone know how many calories are burned doing P90X?

I typically burn between 450 and 600 calories per workout depending on how hard I workout.

The last month or so my HRM battery has been dead and I haven't replaced it...but I have discovered that the MFP calculations for "circuit training - general" are very close to what my HRM would say on an average day with P90X.

I take out the Plyo and Kenpo and do Turbo Kick rounds, so I don't know really how many cals I burn during those X workouts.

I just log the Yoga X as "yoga." It burns about 250-300 calories in 90 minutes for me.

Invest in a HRM and stop guessing. Our caloric burns aren't going to be the same as yours. I burn ~800 - 1000 calories, while someone else could only burn ~400.

Nicely put, and oh so true.
Heck I've seen as much as 25% swings between the same workouts over a couple of weeks just because I pushed harder some days than others. Anything other than a measured burn (HRM or Bodymedia Fit/BodyBugg etc) is just going to be a guess, and unless you're factoring in age/weight/gender/fitness level/motivation level, it's probably not even going to be an educated guess...