I bought a new hrm, it shows calories burned, but the calories seem really high. My treadmill shows 220 for 1/2 hour walking while the hrm shows 447. Both numbers seem off to me, which do I go by?

Hm, both of those numbers seem pretty high to me. The standard I go by for running on the treadmill is 100cals/mile, which should be about the same for walking. In 1/2 hour, you prob walk a little under 2 miles, right? So I would say you're burning a little under 200 cals, but I know it varies for body weight and how trained your body is, so if you're very new to exercise, you could be burning more than that until your body adapts. Hope that helps!

Thanks!

Treadmill #s tend to be less off if you've entered your weight into them (Can do this on some but not all models) but its usually a little high. 100/mi is for average weight people I seem to tend to burn closer to 400 but I walk very briskly. Other equipment like elliptical tend to WAY over estimate.

I think you should get your HRM checked, recalibrate it, I don't have one though so I'm not sure if that's possible. if it's new, exchange it and see if the new one gives you the same number.

brave - it seems as though the TM is more accurate. IT is an avg of about 100/mile however that also depends on your bodyweight...meaning you may be a little higher than that. And as Ilene suggested I would exchange the HRM and test it. The HRM seem off.

I took the hrm back to the store, I know there is no way I burned that many calories in 30 minutes, as much as I would love to. I guess I will just stick to the treadmill for now.

Honestly the rule of thumb is to work your tail off. Any monitor telling you how many calories you burn is inaccurate. The closest thing (which is still horribly inaccurate) is the expensive heart rate monitors you wear around your chest.