how accurate is my hrm???

MoNiCaMaRieV

ive been using the sportline universal hrm and i use the chest strap everytime i workout... i was just wondering if should be logging the full amount of calories it says i burn... i used my elliptical here at home for about 20 min and my hrm says that was 402 cals burned i was switching the intensity levels also.. should i trust the numbers it gives me should i be subtracting some of those you think? im 5'6 139 lbs... i did circuit training for 10 min and burned a little over 100 cals... it just seems like im burning a high amount of cals ALL the time in less than 40 min dont know how much i should trust it....advice plz?