Work out heart rate variability instantly with clear inputs, formula shown and shareable results.
RMSSD is the root mean square of successive differences between heartbeats and is the standard short-recording measure of parasympathetic activity. Because it is log-normally distributed, apps report the natural log scaled to a 0-100 score - 20 x ln(RMSSD) here. RMSSD declines roughly 0.5 ms per year after age 20, so comparisons must be age-adjusted.
HRV score
score = 20 x ln(RMSSD)
Age expectation
typical RMSSD is about 60 - 0.5 x (age - 20) ms
This is an estimate from population-average equations, not a medical or diagnostic assessment. Individual results vary with genetics, training history and technique. Seek advice from a qualified coach or clinician before making significant changes to training.
Because raw RMSSD is heavily skewed, so a 10 ms change means something very different at 20 ms than at 80 ms. Logging makes changes comparable.
The trend against your own baseline. Absolute HRV varies enormously between individuals and is nearly useless for comparison.