HRV Index Calculator

How to calculate HRV Index?

HRV index is a logarithmic transformation of RMSSD, often adjusted for heart rate to better reflect parasympathetic activity.

Formula: HRV Index = 10 % ln(RMSSD)

Using the HRV Index: an example

Example: A user with an RMSSD of 45ms and RHR of 60bpm.

Step-by-step calculation:

1. Input RMSSD value of 45
2. Apply natural log: ln(45) ≈ 3.81
3. Multiply by 10 to get an Index of 38.1
4. Compare to baseline for recovery status

Frequently Asked Questions

Why normalize for Heart Rate?

RHR and RMSSD are physiologically linked; normalization ensures the index reflects nervous system status rather than just heart speed.

How do wearables differ?

Different devices use varying sampling rates and algorithms (e.g., SDNN vs RMSSD), leading to unique baseline 'normal' ranges.

When is the best time to measure?

Consistency is key; measure immediately upon waking while still in bed for the most accurate ANS assessment.