As we all know, treadmill and other exercise equipment will over estimate calories burned and sometimes significantly. Mine, a nordik trac model, will show 20+% more than actual depending on the duration. The distance measurement on the treadmill tho is right on, as at a 1% incline (to better equate to actual walking) for one mile the calorie counter on the HRM showed 104 calories. I weigh 183, and as we all know a 180 lb person moving on flat terrain for one mile, regardless of speed, burns about 100 calories. I was glad to see that equality.
Anyway, I have a HRM and i hope to put it to good use so I can be a little closer to the actual calorie burn than even a good guess might be!