What Is a Good HRV? Heart Rate Variability Explained by Age

There is no single good HRV. In healthy adults, a short resting reading of RMSSD, the most common HRV measure, usually falls between about 19 and 75 milliseconds, and it drops with age. A good HRV sits within your own normal range or trends upwards over weeks. Sudden falls below your baseline matter more than the number itself.

Below: what HRV is, how it is measured, normal ranges by age, and what pushes it up or down.

What is heart rate variability?

Your heart does not beat like a metronome. Even at 60 beats per minute, the gap between one beat and the next might be 0.95 seconds, then 1.05, then 0.98. Heart rate variability (HRV) is the measure of that beat-to-beat variation, recorded in milliseconds (ms).

The variation comes mostly from your autonomic nervous system, the part of the nervous system that runs without you thinking about it. It has two branches. The sympathetic branch speeds the heart up for effort and stress. The parasympathetic branch, driven largely by the vagus nerve, slows it down for rest and recovery. When you are relaxed and well recovered, the parasympathetic side has more influence and the gaps between beats vary more. When you are stressed, ill, under-slept or still recovering from a hard session, the heart beats more evenly and HRV tends to fall.

The methods used to measure HRV were standardised in 1996 by a joint Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. That report is still the reference point for how HRV should be recorded and interpreted.

How is HRV measured?

There are dozens of HRV metrics, but two appear most often:

• RMSSD (root mean square of successive differences): looks at how much each beat-to-beat interval differs from the next. According to a widely cited review of HRV metrics and norms by Shaffer and Ginsberg, RMSSD is the primary time-domain measure used to estimate vagally mediated changes in HRV. Most wearables that show a single HRV number use RMSSD or something close to it.
• SDNN (standard deviation of normal-to-normal intervals): measures overall variability across the recording. It is used more in clinical 24-hour recordings.

How long and when you record changes the result. The same review cautions that 24-hour, short-term (about 5 minutes) and ultra-short-term values are not interchangeable. A 5-minute reading taken lying down first thing in the morning will not match an overnight average, and neither will match a reading taken at your desk after coffee. That is why two devices can show you different HRV numbers on the same day, and why you should only compare readings taken the same way. If you are new to wearables, our guide to what a smart ring is and how it works explains how optical sensors read your pulse.

What is a normal HRV for adults?

The best-known reference for short-term HRV in healthy adults is a systematic review by Nunan and colleagues, which pooled 44 studies involving 21,438 participants. For 5-minute resting recordings, it reported:

Two points stand out. First, the values in the literature were lower than the norms suggested in the 1996 Task Force report. Second, the authors found very large differences between individuals, which is exactly why a population range can only tell you so much.

What is a good HRV for my age?

HRV falls with age. In a study of 260 healthy people aged 10 to 99, Umetani and colleagues found that RMSSD dropped quickly, reaching 47% of its level in the second decade of life (ages 10 to 19) by the sixth decade, and then levelled off. Differences between men and women were present in younger adults and disappeared after 50.

The largest dataset so far comes from a study of more than 8 million Fitbit users published in The Lancet Digital Health. It confirmed that HRV decreases with age, that parasympathetic function declines faster than sympathetic function, and that HRV swings strongly across the day. It found no significant difference between men and women for RMSSD.

The preprint version of that study publishes RMSSD by age, measured from wrist-worn optical sensors between 6am and 7am. The middle column shows the median, and the range covers the middle half of people (25th to 75th percentile):

Read this table with care. The data came from one brand of wrist device, at one hour of the day, in people who chose to wear a tracker. A quarter of perfectly healthy people in every age group sit below the middle band and a quarter sit above it. If you are 45 and your morning RMSSD is 30 ms, that alone tells you very little. What it does after a hard week, a late night or a month of consistent training tells you much more.

Why your own baseline matters more than population norms

Genetics, age, sex, fitness, breathing rate, body position and the device itself all shift your HRV. Two healthy people of the same age can differ by a factor of two or more.

Sports scientists who monitor athletes work the other way round. A review of HRV in elite endurance athletes by Plews and colleagues concluded that longitudinal monitoring is needed to understand each athlete's individual HRV fingerprint, and recommended averaging values across days rather than reacting to single readings. The same paper notes that in very fit athletes, HRV can even fall while fitness improves, which only makes sense against a personal history.

Shaffer and Ginsberg make a related point: the goal is an optimal level of HRV, which is associated with health, self-regulation and resilience. Higher is not automatically better.

In practice, that means:

1. Measure the same way every time, ideally overnight or first thing on waking.
2. Give it two weeks or more to establish your normal range.
3. Look at a rolling average of several days rather than any single reading.
4. Pay attention when your average sits clearly below your normal range for several days in a row, especially alongside a raised resting heart rate or feeling run down.

What lowers HRV?

Most things that put your body under strain push HRV down for a night or longer:

• Alcohol: in a real-world study of 4,098 Finnish employees, alcohol lowered RMSSD in a dose-dependent way during the first three hours of sleep: by about 2 ms after a low intake, 5.7 ms after a moderate intake and 12.9 ms after a high intake. Heart rate rose too. Regular exercise and youth did not protect people from the effect.
• Hard training: intense sessions suppress HRV until you recover. Stacking hard days without recovery keeps it down.
• Short or broken sleep: less recovery time overnight usually means a lower reading.
• Illness: infections and fever raise your heart rate and usually pull HRV down with it.
• Psychological stress: deadlines, arguments and worry show up in your nervous system as well as your head.
• Age: a slow decline over decades is normal and expected.

How can you improve your HRV?

There is no shortcut, but the basics move the needle for most people. Shaffer and Ginsberg note that time-domain HRV measures rise with aerobic fitness, so regular endurance exercise, built up gradually, is the foundation. Beyond that:

• Keep a regular sleep schedule and protect enough time in bed.
• Drink less alcohol, especially on nights before you want to train hard.
• Balance hard days with easy days, and take full rest days when your data and your body both say so.
• Manage stress in whatever way works for you: walking, time outdoors, slow breathing, time off screens.

Expect gradual change over weeks and months, not days.

Is a low HRV a sign of a health problem?

Low HRV is linked with higher cardiovascular risk in large population studies, but a single low reading from a wearable is not a diagnosis. Many healthy people simply sit at the lower end of the range. A consumer HRV reading cannot tell you whether you have a heart condition.

What deserves attention is symptoms. If you notice palpitations that keep coming back, a heartbeat that feels irregular, chest pain, breathlessness or dizziness, speak to your GP, or call 999 if symptoms are severe. For more on using a wearable day to day, our PulseRing FAQs answer common questions about the ring.

Frequently asked questions

What is a good HRV score?

There is no universal good score. For healthy adults, short resting RMSSD readings typically fall between about 19 and 75 ms, with lower values in older people. A good HRV for you is one that sits within your own normal range or rises gradually over weeks as your fitness, sleep and recovery improve.

Is a higher HRV always better?

Not always. Higher resting HRV generally reflects stronger parasympathetic activity and good recovery, but researchers describe an optimal level rather than a maximum. In very fit athletes, HRV can even dip while fitness improves. A sudden, unexplained jump well above your usual range is worth noting, just like a sudden drop.

What is a normal HRV for a 40 year old?

In a study of millions of Fitbit users, the median morning RMSSD at age 40 was about 37 ms for women and 38 ms for men, with the middle half of people between roughly 26 and 54 ms. Plenty of healthy 40 year olds sit outside that band, so your own trend matters more.

Why is my HRV different on two devices?

Devices use different metrics, different measurement windows and different algorithms. An overnight average, a 5-minute morning reading and a daytime spot check will not match, even on the same person. Pick one device, measure the same way each time and compare yourself with your own history rather than across brands.

How long does it take to see your HRV baseline?

Most people need around two weeks of consistent readings before their normal range becomes clear, because HRV moves a lot from night to night. PulseRing Pro builds its personal baseline over roughly two weeks of wear. After that, the trend across several days is more useful than any single night.

This article is for general information and is not medical advice. PulseRing Pro is a wellness device, not a medical device, and does not diagnose or treat any condition. If you are worried about your health, speak to your GP or a qualified clinician.