HRV is the number every wearable now shows and almost nobody interprets correctly. People see 34 ms one night and 78 ms the next and either panic or feel elite. This guide explains what heart rate variability is, what the published averages by age actually say, why Apple Watch, Whoop, Oura, Fitbit and Garmin readings cannot be compared, what genuinely moves the number, and how to use it as a training signal without letting it run your life.
Disclosure: Fitcoin is our product. We are not affiliated with Whoop, Oura, Google, Fitbit, Garmin, Polar, Amazfit, Xiaomi, Samsung, Ultrahuman, RingConn, Hume Health, Bionny, Apple or any other hardware brand named here. We do not sell trackers and we take no affiliate commission. Where Fitcoin appears, it is as the rewards and insights app that reads the data these devices write to Apple Health or Health Connect. Everything below is a wellness estimate for general fitness, not medical advice.
The short answer
A good HRV is one that is normal or rising for you. Population averages exist and we print them below, but they span a huge range at every age: Fitbit's analysis of 8 million users found average overnight HRV falling from around 60 ms at 25 to around 31 ms at 60, with healthy people scattered far above and below both numbers. Genetics, age and how your device measures it matter more than fitness. Compare tonight with your own 30 to 60 day baseline, and treat a sustained drop alongside a rising resting heart rate as the signal to ease off.
What HRV actually is
Your heart does not beat like a metronome. At 60 beats a minute the gaps between beats are not all exactly one second; they might run 0.94 s, 1.06 s, 0.98 s. Heart rate variability measures how much those gaps vary. Counter-intuitively, more variability at rest is usually the healthy direction. It reflects a nervous system that can flex between rest-and-digest (parasympathetic) and fight-or-flight (sympathetic) modes. Stress, illness, alcohol, poor sleep and heavy training tend to suppress it.
HRV is a marker of autonomic balance, not a fitness score. Two equally fit people can sit at 35 ms and 95 ms for life. What changes with training, recovery and health is where you sit relative to your own norm, which is why every serious wearable draws a personal range and every serious coach ignores the raw milliseconds.
Why your device's number is not comparable to your friend's
HRV is a family of calculations, and wearables do not all use the same one:
| Device | Formula | When it measures | Baseline it compares to |
|---|---|---|---|
| Apple Watch | SDNN | Spot samples when still, plus overnight in Vitals; every five minutes on Series 12 and Ultra 4 | Personal range in Vitals |
| Whoop | RMSSD | During the deepest sleep | Rolling personal baseline, roughly two weeks |
| Oura Ring | RMSSD | Averaged across the night | Personal baseline for Readiness |
| Fitbit / Google Health | RMSSD | Longest sleep period | 30-day personal range |
| Garmin | RMSSD (five-minute averages) | Overnight | Three-week baseline for HRV Status |
SDNN and RMSSD are different statistics. SDNN, the standard deviation of all normal beat intervals, typically produces higher numbers than RMSSD, the root mean square of successive differences, over the same night. That alone explains most of the gap between an Apple Watch reading of 65 ms and a Whoop reading of 45 ms on the same sleeper. Neither is wrong. They are measuring different things at different times.
Device-specific guides: HRV on Apple Watch, Fitbit HRV, and the Whoop Recovery page for how Whoop weights it.
Average HRV by age
The best-known large dataset comes from Fitbit, which published average overnight RMSSD from around 8 million users. The pattern is the same in every published cohort: HRV declines with age, faster in the twenties and thirties, more slowly after 50, with a wide spread at every age.
| Age | Approximate average overnight HRV (RMSSD) | Typical spread |
|---|---|---|
| 20 to 25 | Around 55 to 65 ms | Roughly 25 to 100+ ms |
| 26 to 35 | Around 45 to 55 ms | Roughly 20 to 90 ms |
| 36 to 45 | Around 38 to 48 ms | Roughly 18 to 80 ms |
| 46 to 55 | Around 32 to 40 ms | Roughly 15 to 70 ms |
| 56 to 65 | Around 28 to 34 ms | Roughly 12 to 60 ms |
| 65+ | Around 25 to 30 ms | Roughly 10 to 55 ms |
Men tend to read slightly higher than women on RMSSD at the same age, athletes higher than sedentary people, and genetics account for a large share of the difference between individuals. None of these effects is large enough to make a single reading meaningful.
What actually moves HRV
Down
- Alcohol. The most reliable suppressor in every wearable dataset. Two drinks can drop overnight HRV by 10 to 20 percent and raise resting heart rate for the whole night.
- Illness. HRV often falls a day or two before symptoms appear, which is why temperature-plus-HRV illness flags on Oura and Whoop work at all.
- Hard training. A big session or a heavy week suppresses HRV the following night. That is normal; it should rebound within a day or two.
- Poor or short sleep. Both the night itself and the debt carried into it.
- Late meals, heat, dehydration, travel, stress. Individually small, cumulatively obvious.
Up
- Consistent aerobic training over months. The one lever that raises the baseline rather than the night.
- Regular sleep timing. Consistency moves HRV more than an occasional long night.
- Fewer drinks, earlier dinners. The two changes people see in their data within a week.
- Recovery from a training block. A deload week often produces the highest readings of the year.
How to use HRV without misreading it
- Ignore any single night. Look at seven-day and 30-day trends.
- Pair it with resting heart rate. HRV down and resting heart rate up on the same night is a real signal. HRV down alone is noise until it repeats.
- Keep the measurement consistent. Same device, same wrist or finger, worn every night. Switching devices resets the baseline.
- Let the app do the comparing. Fitbit's personal range, Apple's Vitals band, Whoop's baseline and Garmin's HRV Status all exist so you do not have to remember what normal is.
- Decide in advance what you will do with a low reading. Swap intervals for an easy session, go to bed earlier, skip the drink. If a low reading never changes behaviour, stop looking at it.
This is exactly what recovery and readiness scores automate. Whoop Recovery, Oura Readiness, Garmin Training Readiness, Fitbit Daily Readiness and Fitcoin's Recovery all take overnight HRV against your baseline, add resting heart rate, sleep and sometimes temperature, and compress the answer into one number. The vendor-neutral explanation is recovery scores explained.
Which wearables measure HRV best
For overnight HRV, any current device with a validated optical sensor is adequate as long as you wear it every night: Oura Ring 5, Whoop 5.0, Garmin CIRQA, Polar Loop, Fitbit Air, Hume Band 2.0 and recent Apple Watches. Rings and bands have an advantage over watches because people actually sleep in them. Apple Watch Series 12 and Ultra 4 closed the gap in September 2026 by measuring HRV as often as every five minutes and splitting it into Recovery HRV and overall HRV; see Series 12 Readiness.
For spot HRV with clinical-grade accuracy, a chest strap such as the Polar H10 paired with an app like HRV4Training beats any wrist or finger sensor; our HRV4Training review covers the morning-reading method. Apple Watch owners who want a dedicated HRV dashboard should read best HRV apps for Apple Watch.
When HRV is not the right tool
HRV is a wellness metric, not a diagnostic one. Consumer devices are not validated to detect arrhythmias through HRV; that is what ECG features on Apple Watch, Fitbit and Whoop MG exist for. Persistently very low HRV with symptoms is a reason to see a clinician, not to buy a different tracker. And for people whose relationship with data tips into anxiety, the healthiest setting is often to hide the number and let a recovery score summarise it.
Frequently asked questions
What is a good HRV for my age?
Averages fall from around 60 ms in the mid twenties to around 31 ms at 60 in Fitbit's 8-million-user dataset, but the spread at every age is enormous. A good HRV is one that is stable or rising against your own 30 to 60 day baseline.
Is an HRV of 30 bad?
Not by itself. Thirty milliseconds is close to average for people in their fifties and within the normal range for many younger adults. It is only a concern if it represents a sustained drop from your own usual level, especially alongside a higher resting heart rate.
Why is my Apple Watch HRV higher than my Whoop or Oura HRV?
Apple Watch reports SDNN, which typically produces higher values than the RMSSD formula used by Whoop, Oura, Fitbit and Garmin. The devices also sample at different times. The numbers are not comparable.
Does a higher HRV mean I am fitter?
Loosely, and only within one person over time. Consistent aerobic training raises your baseline over months. Between people, genetics and age dominate, so a fitter person can easily have lower HRV than a less fit one.
How quickly can I raise my HRV?
Removing alcohol and fixing sleep timing shows up within a week. Raising your long-term baseline through aerobic training takes months. Nothing raises HRV meaningfully overnight except recovering from whatever suppressed it.
Should I train when my HRV is low?
One low night is not a reason to skip training. A low reading that repeats for two or three nights, particularly with an elevated resting heart rate, is a sensible cue to swap a hard session for an easy one and prioritise sleep.
Method: Checked September 26, 2026 against manufacturer product pages, published help documentation and independent reviews. Prices are US list at publication unless noted. Fitcoin has no commercial relationship with the hardware brands named here. Wellness estimates only, not medical advice.
Related reading: HRV on Apple Watch, Fitbit HRV explained, Recovery scores explained, Whoop Recovery explained, Best HRV apps for Apple Watch, How many steps a day
About the author: Harris Khan is the co-founder and CTO of Fitcoin, a UK fitness-rewards and health-insights app that reads Apple Health and Health Connect.