Unfortunately the algorithms used to set up heart rate monitors are not designed to measure anything other than steady sate work making them inaccurate and not capable of monitoring work done during strength training. In addition when done properly strength training has a carry over effect called exercise post oxygen consumption (EPOC) which means you are continuing to have an elevated metabolic rate following strength training which continues to use calories. The EPOC renders the values of a heart rate monitor as not meaningful for strength training. Even for cardio they will only produce guesstimates since the algorithms are based on a standard bell shaped curve meaning 25% of any population will fall at one or the other end of the curve.
To increase the degree of accuracy as to your calorie count monitor calories in not out, you can not out exercise a bad diet.
It is called WORK-ing out for a reason.
I said getting fit was simple, I did not say it was easy.
Cardio burns calories, strength work burns fat.
Eat well to lose weight, exercise to get fit
You can not build a six pack using twelve packs
Often when we seek a magic bullet for fitness we end up shooting ourselves in the foot.
"I think calories are little germs in food that all moms are afraid of" Dennis the Menace