I have been using a HRM that I purchased relatively recently, and when I compared calories burned on HRM to "circuit training, general" calories calculated by MFP, I found out that MFP substantially overestimates the amount burned. For me, the difference was even as much as 150-180 cals per 30 minute workout. I would strongly recommend that you purchase a HRM if you want to know the exact amount burned.

If you don't want to invest in a HRM, I guess the circuit training option would be the best choice, but bear in mind the actual amount burned is probably less.

You're welcome, any time. I bought Polar FT4 from http://www.heartratemonitorsusa.com. They are right now $65 and have free shipping. They have specials from time to time, and I think I got mine on sale. I am pretty happy with it. It does what I need it to do. They also have less expensive FT1 and FT2, and more expensive and more complicated ones. I studied the descriptions on the website, and FT4 seemed like the best compromise between the price and functionality for me. It seems that a lot of people on MFP use a Polar.

For JMBR Cardio workouts, it is usually up to 250 (e.g., yesterday in the evening it was 204 and this morning 225 for the same workout), and for the remaining ones usually somewhere between 250 and 325. Some of the workouts are shorter than others, so I assume that will also account for the difference in calories burned.

My hrm calorie burn doesn't do well...not an expensive model....it does give me a good indicator of ave hr during the workout for which I plug it into a formula that gives me cals...it gives me in this same range also....

Ive got the polar ft4 too and love it, average burn for any of the weights workouts is around 250 for me (however i then deduct what i would normally burn if i wasnt working out which for me is 120 cals) so i dont overestimate cals burned.