So, I started using a HRM for my workouts because I think MFP is a little too kind on the amount of calories it says we burn for an activity. I thought my HRM was being too stingey (sp?) so I found a website to calculate calories burned per workout based on heart rate and your weight. My HRM is pretty darn close so I guess I'll trust it from now on and workout a little harder. lol
http://www.livestrong.com/article/78365-estimate-calories-burned-heart-rate/