I've had a Polar heart rate monitor for a little over six months. I love exercising with it on and somehow it keeps my motivation going and makes me push myself as much as possible. My only issue with it is I don't know how accurate it is in terms of the calories burnt - I know it'll be more accurate than gym equipment, but I'm still not convinced the calories burnt are as high as it says. For example, if I run at a fairly intense pace for one hour (75% of MHR) then it will say I've burnt 800 calories. I'm skeptical of this, so I usually count it as 550-600 calories. Most days I aim to burn 700 calories through cardio.

What I do to calculate how many calories I've burnt is take off what I would usually burn in an hour just being sedentary. I usually burn 150-200 per hour being fairly sedentary. So if I run for an hour and a half - burn 1050 calories per my heart monitor, then I take off approx 250 per hour (200 because I would burn that if I wasn't exercising and 50 to make up for Polar HRM overestimation.)

If I want to burn 1000 I work out to 1450-1500
If I want to burn 700 I work out till 1000
If I want to burn 500 I work out 750-800
If I want to burn 200 I work out to 350 (approx.)

Does this sound accurate? I am a calorie counter and I've worked out that I lose the most weight when eating about 1900 and burning 700 off. So I'm trying to make sure my calculations are as accurate as possible.

Hmmm. One thing that I learned from wearing a HRM is that I got kinda obsessive about the numbers. It's cool to know how many calories you're burning through exercise, but I never adjusted the calories that I ate by how much I burned. I just ate X amount of calories per day.

How accurate is it? I think a HRM is the most accurate measure that we have for at home use.

I read that they have a 10% margin of error. I wear one - use the results and compare those to my calorie counts. BUT - no need to split hairs. Take what it says and go with it.