Calories burned are way off on MyFitnessPal?

Calories estimations from activities that are not aerobic in nature plainly sucks, with online tools, MFP, and especially with HRM. HRM assumes that your heart rate is elevated in direct correlation with increased VO2 consumption, and that part is not true for most activities that are not aerobic.

Weight lifting, 30 day shred... while your heart rate increases with those activities, the HRM is THE WORST possible estimation for them, since your HRM always assumes (from it's formula) that your VO2 increases as well. For those cases, rigorous online tools that are backed up by specific sources for those activities are more reliable.

HRMs for weight lifting is indeed a gimmick, but if you are training for endurance sports, they are as invaluable as a pair of running shoes. Sure you can do without, but there is no way it will be as efficient

ive looked up the calories burned doing the exercises at light, moderate, vigorous and very vigorous that i do and take an average between the 2 (my calculation and mfp's). i map my runs on g map pedometer and that also calculates calories for my weight, i also calculate my pace when ive been running so i can judge it on that also and of course im honest about how hard i work! it seems to be working im upto 17lb loss :-)

I've always used estimates from either MFP or Runkeeper (no heart rate there, just speed and distance) and those numbers have worked out just fine for me, I lost weight at pretty much the rate I chose as long as I ate the suggested net calories (which means eating the base amount plus the extras from exercise).

Everything we add (food and exercise) is an estimate, as is the amount of calories MFP suggests you eat.
I don't think the fact that you can't guarantee the accuracy of MFP calories is a good reason not to log (and eat!) them. But then, I'm not a fan of setting myself up to fail by deprivation.

I suggest that you accept that everything is an estimate, run with it for a month and see how your body responds. If you are losing weight too fast or too slow (assuming you have set a realistic goal) then you can change things around as needed.

Oh my gosh, you guys are FABULOUS! I really feel like I've found a home here. Thanks for the great advice and for so many responses to my question!

Don't get too used to receiving useful, relevant information from the MFP forums. It doesn't happen very often.

When I bought my exercise bike a few weeks ago and spent 10 mins on it at a rate of about 25km per hour it said I had used over 250 calories........Brilliant I thought, then my HRM arrived and when I used that for the next 10 minutes it showed I'd actually only used 40 calories!!!....and i'm afraid that I know that it is a more realistic view......just think what would have happened to my weight if I'd eaten back the "bike" calories which were 210 more than actually used!!!