is my HRM accurate??

Fat2FitAmanda

This is not to sound bratty in any way, I'm just wondering something. I know that everyone's burn is different and there are a lot of factors that go into how many calories are burned in a workout, BUT, I'm seeing a lot of my friends (sorry for calling you guys out!) on here doing the same workouts as I am/have and they seem to be burning a whole LOT more calories than I am. I don't feel like I'm slacking in my workouts or anything so I don't think it's because I'm not working as hard as them. Another thing that makes me question if I'm getting the right calories burned, is I have the EA Sports Active 2 game with the HRM and the calories never match. My Polar is actually telling me I'm way higher than what the game HRM is telling me. I did just recently update my weight in my HRM but I know there's something that I never figured out what it was....I believe it's an o2 sensor or something?? Do I have to do something with that to make it calculate more accurately? If anyone has any explanations for me, please let me know! Thanks!