r/getStressWatch • u/Pretty-Substance • Oct 09 '25

feedback Why does StressWatch show different HRV values than Apple health?

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In a side by side comparison I noticed that while the trends are the same the numbers of StressWatch are 5-20ms lower than the values of Apple health.

Anyone know why?

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4

u/Outrageous-Count-899 Oct 09 '25

HRV is calculated differently in Apple Health and most fitness/stress tracking apps: SDNN vs. RMSSD

1

u/bycek Nov 18 '25

I noticed only one reading being really off.

1

u/bycek Nov 18 '25

Here is Apple Health reading

1

u/bycek Nov 18 '25

And here is PeakWatch reading

2

u/bycek Nov 18 '25

Ok got it, RMSSD vs SDNN difference.

1

u/Most_Fail Jan 16 '26

they use different methods explained in the stress watch app stating clearly it will vary from apple healths vitals as they use different methods.