Question: how accurate is the heart rate monitor on fitbit alta hr?
Answer: Compared to that measurement, the Apple Watch overestimated the average by 1 beat (161 bpm), and the Fitbit Alta HR underestimated by 3 bpm, which is pretty impressive and consistent with Fitbit's claim of average absolute error of less than 6 bpm versus an EKG (electrocardiograph) test strap.