There is no HRV value that is good for everyone. The figures you find online run from 20 to over 150 ms, and that is not because people differ that much. It is because those numbers describe different metrics recorded over different windows.
A 24-hour SDNN and an overnight RMSSD are not versions of the same number.
This is what has bothered me about HRV pages for years: they print a range without saying which metric it is, how long the recording ran, or in whom. Without those three things you cannot place your own value beside it.
Why do HRV values vary so widely?
Because three choices set the number before your heart has anything to do with it. The metric chosen, the length of the recording and the population studied. Change one and the number shifts by tens of milliseconds with no physiological change at all.
Recording length is the biggest culprit. SDNN over 24 hours also captures your day-night rhythm and your training peak, so it lands far higher than an SDNN over five minutes (PMID 8598068). RMSSD is far less sensitive to this.
| Metric | Recording window | What it mainly reflects | Comparable to your watch? |
|---|---|---|---|
| SDNN | 24 hours | Total variation including day-night rhythm | No, lands far higher |
| SDNN | 5 minutes | Short-term variation, both branches | Partly |
| RMSSD | 5 minutes or overnight | Mainly parasympathetic activity | Yes, this is what most devices show |
| pNN50 | 5 minutes or overnight | Same direction as RMSSD, coarser | Rarely displayed |
| Ln(rMSSD) | Overnight, 7-day average | Trend without the daily noise | Only in training apps |
If your device shows a number around 45, that is almost certainly RMSSD. Which metric you should actually follow sits in RMSSD or SDNN.
What is a normal HRV value?
In healthy adults, overnight RMSSD often falls somewhere between 20 and 90 ms, with an average around 40 to 50 (PMID 29034226). That range is wide because it genuinely is wide. Someone of 25 and someone of 60 do not belong in the same band.
The largest pooled analysis to date combined 44 studies covering 21,438 participants and found reasonable agreement between studies for the common metrics (PMID 20663071). Reasonable, not exact. Even within healthy groups the spread stays large.
So this is the only sensible rule. Your own average across fourteen nights is your normal value, and everything after that is measured against it.
How does HRV change with age?
It falls, but not every metric falls at the same rate, and that is the interesting part. The best study on this followed 260 healthy people aged 10 to 99 with 24-hour recordings and found clearly different patterns per metric (PMID 9502641).
This table summarises that work, expressed as a percentage of the youngest group.
| Metric | Pattern | Remaining | Reached by |
|---|---|---|---|
| SDNN and SDANN | Gradual decline | 60 percent | Tenth decade |
| SDNN index | Linear decline | 46 percent | Tenth decade |
| rMSSD | Steep, then flat | 47 percent | Sixth decade |
| pNN50 | Steepest, then flat | 24 percent | Sixth decade |
Read those bottom two rows again. RMSSD and pNN50 lose most of their value before you turn sixty and stay fairly stable after that. So the familiar line that your HRV declines steadily until you die does not hold for the metric your watch shows.
Does HRV differ between men and women?
Under thirty it does, above that barely. In the same study, all HRV metrics were lower in women under 30 than in men. That difference shrank after age 30 and had disappeared by around 50 (PMID 9502641).
Practically it changes little about your approach.
You compare yourself to your own baseline anyway, not to a group average. At most it explains why a 26-year-old woman worries unnecessarily about a number that suits her fine.
What is a good HRV value for athletes?
Trained endurance athletes show higher values as a group than non-athletes, but the overlap is enormous. A well-trained rower can sit at 45 ms and an office worker at 70. Both are normal, and neither says anything about their fitness.
Imagine two runners who both sit at 52 ms. One came up from 38 in three months, the other dropped from 71. Same value, opposite direction, and only the direction is usable information.
What does reliably reflect your fitness is your VO2max, and what reflects your recovery is your resting heart rate alongside your HRV. The Dutch Hartstichting uses 60 to 100 beats per minute for that resting rate, with lower values in trained endurance athletes.
Can you compare your watch value to these tables?
Not directly, and that is a bigger problem than most articles suggest. The figures above come from ECG recordings under research conditions. Your watch measures with an optical sensor on your wrist, during sleep, with its own algorithm.
Research placing six consumer devices next to a reference measurement found that agreement differs per device (PMID 36016077). They are usable for following your own trend, but not for holding your number up against a published table.
My advice stays the same as with any wearable: pick one device, keep it for six months, and compare only with yourself. What the different brands actually do sits in HRV status on Garmin.
If your value stays below your own normal for weeks, a look at your blood makes more sense than another table. Ferritin and TSH are the two that most often explain something in athletes, and both sit in InsideTracker.
Every blood test result includes a professional assessment from a BIG-registered doctor. For treatment decisions, discuss your results with your GP.
References
- Umetani K, et al. Twenty-four hour time domain heart rate variability and heart rate: relations to age and gender over nine decades. Journal of the American College of Cardiology, 1998. PMID 9502641.
- Shaffer F, Ginsberg JP. An overview of heart rate variability metrics and norms. Frontiers in Public Health, 2017. PMID 29034226.
- Nunan D, et al. A quantitative systematic review of normal values for short-term heart rate variability in healthy adults. Pacing and Clinical Electrophysiology, 2010. PMID 20663071.
- Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. Heart rate variability: standards of measurement, physiological interpretation and clinical use. Circulation, 1996. PMID 8598068.
- Miller DJ, et al. A validation of six wearable devices for estimating sleep, heart rate and heart rate variability in healthy adults. Sensors, 2022. PMID 36016077.
- Hartstichting. Resting heart rate.
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