Heart rate monitors: are they on crack?

I wear a HRM when I exercise that "keeps track of calories I burn." I put that in quotes, because I am wondering if the numbers I see at the end of a workout are ACTUAL, or just some whacked-out nonsense that the HRM makes up. A 75-minute workout (20 minutes medium-intensity on the bike, the rest in weights) shows an average burn of 800 calories, with my HR between 115 and 145.

Is that kind of burn possible??? BTW, it's a Timex HRM with a chest strap, so it's supposed to be more accurate than a non-strap type.

It's my understanding that the burn is COMPLETE heart rate (not just the range you set).  Meaning when I workout for say 60 minutes, my range is 110 to 150 and my HRM will tell me I was ONLY in that range for 30 of the 60 minutes.  My calorie burn is for the WHOLE 60 minutes not just when I was in range.

Ms Shell

That's basically what mine tells me (time in target range (usually about 3/4 of the length of session), average, peak and cal burn) but the calories burned are always at least 650.

Then that's YOUR burn darlin.  I mean when I do different exercises like weights it's significantly lower then when I do the eliptical, treadmill or aerobics class.

Yep... I'd say pretty accurate.  I use a Polar and LOVE It

It really depends.

Different HRMs use different algorithms to calculate burn  but they are all fairly close, in additions some HRMs can be set to use different base information as the refference point.  Height Weight calcs will give one number which is an average for people in that demographic, when you add in HR you get more accurate because My HR at 5mph can be different than your HR at that speed even if we are the same height and weight.  Really good HRMs can use a metabolic profile which will affect the numbers again because there is a difference in Aerobic and Anaerobic and calories burned at various heart rates.

would I believe 800 calories for 75min? yes I would As others have said if you can alayze by interval you will/should see your largest burns happening at your higher hear rates.

Here is one of my interval sessions

You can see the recovery HR (lower avg hr) has a lower calorie burn, I point out the intervals laps that were 4min because they are consistent in speed and the hr range is a target so it is easy to compare.

Now if you are trying to see what you burns are for various activities, it is fairly simple if you have a lap button just start a new lap or start a new workout session and save the previous one.