A good heart rate variability depends heavily on your age, but as a general benchmark, an RMSSD (the metric most wearables report) between 40 and 100 milliseconds is typical for healthy adults under 40, while values above 50 ms in your 30s or above 35 ms in your 50s suggest solid cardiovascular fitness. The single most important thing to understand about HRV is that your personal baseline matters more than any universal number.
What HRV Actually Measures
Your heart doesn’t beat like a metronome. Even at rest, the gap between one beat and the next varies slightly, sometimes by tens of milliseconds. Heart rate variability captures those tiny fluctuations. A higher HRV means your heart is responsive and flexible, adjusting its rhythm moment to moment. A lower HRV means the intervals between beats are more rigid and uniform.
This variation is controlled primarily by the vagus nerve, the main cable of your parasympathetic (“rest and digest”) nervous system, which runs from your brain to your heart. When vagal tone is strong, your heart speeds up slightly as you inhale and slows down as you exhale. This natural rhythm, called respiratory sinus arrhythmia, is one of the clearest signs that your nervous system is functioning well. Higher HRV reflects a body that can shift smoothly between stress responses and recovery.
Typical Ranges by Age and Sex
HRV declines steadily with age. This is normal and expected. Data from wearable devices shows clear patterns across age groups, measured in RMSSD (milliseconds):
- Teens to late 20s: Men roughly 55 to 100 ms, women roughly 55 to 90 ms
- 30s: Men around 56 ms, women around 53 ms
- 40s: Men around 43 ms, women around 42 ms
- 50s: Both sexes around 34 ms
- 60 and older: Typically 25 to 45 ms for most adults
These are averages. Among 25-year-olds tracked by WHOOP, the middle 50% ranged from about 50 to 100 ms for men and 45 to 90 ms for women. That’s a wide spread even within the same age group. Young endurance athletes at rest can exceed 200 ms, while a sedentary but otherwise healthy adult might sit below 20 ms. Both can be “normal” depending on context.
The sex difference is small and largely disappears after age 50. If your number sits within or above the average for your age bracket, that’s a positive sign. If it’s below, that doesn’t necessarily mean something is wrong, but it’s worth paying attention to trends over time.
Why Your Personal Baseline Matters Most
Comparing your HRV to population averages gives you a rough idea of where you stand, but the real value of tracking HRV is watching how your own number changes over weeks and months. A consistent upward trend suggests your body is adapting well to training, sleep, and stress. A sustained drop, especially one that lasts more than a few days, often signals that something is off: accumulated fatigue, poor sleep, illness brewing, or chronic stress.
Day-to-day swings are completely normal and not worth worrying about. Your HRV follows a circadian rhythm, peaking during deep sleep (parasympathetic activity is highest around 2:00 a.m.) and dropping during waking hours. That’s why most wearables measure HRV during sleep or immediately upon waking, when conditions are most consistent. A reading taken after your morning coffee or a stressful email will look very different from one taken at rest.
What Lowers HRV
Alcohol is one of the most reliable HRV suppressors. Just two drinks can drop RMSSD by 28 to 33% compared to baseline, while simultaneously shifting the nervous system toward sympathetic (“fight or flight”) dominance. This isn’t subtle: the ratio of sympathetic to parasympathetic activity roughly doubles after two glasses of wine or the equivalent in pure alcohol. One drink, interestingly, shows no measurable effect.
Other common factors that push HRV down include poor or short sleep, dehydration, acute illness, overtraining without adequate recovery, and sustained psychological stress. These effects are temporary in most cases. Your HRV will typically bounce back once the stressor is removed, which is part of what makes it useful as a daily check-in on recovery.
What a Low HRV Means for Health
Chronically low HRV isn’t just a fitness metric. It correlates with real health outcomes. In the ARIC Study, a large population-based study published in the American Heart Association’s journal Circulation, people in the lowest third of HRV had roughly double the risk of cardiovascular death compared to those in the middle range. Specifically, those with the lowest RMSSD values had a 95% higher relative risk of cardiovascular mortality and a 73% higher risk of death from all causes.
This doesn’t mean a low reading on your watch predicts heart disease. These findings come from clinical recordings in large populations and reflect chronically low HRV in combination with other risk factors. But they do underscore that HRV isn’t just a wellness buzzword. It reflects something real about how well your autonomic nervous system is functioning, and a consistently low reading over months or years is worth taking seriously, especially alongside other cardiovascular risk factors like high blood pressure, inactivity, or smoking.
How to Raise Your HRV
Aerobic fitness is the single biggest lever. Regular cardiovascular exercise, even moderate-intensity walking or cycling, strengthens vagal tone over time. This is why endurance athletes tend to have dramatically higher HRV than sedentary people of the same age. You don’t need to train like an elite athlete to see gains. Consistent moderate exercise over several weeks typically produces a noticeable upward trend.
Sleep quality is the second major factor. Deep, uninterrupted sleep is when parasympathetic activity peaks and your body does its heaviest recovery work. Anything that fragments sleep, whether it’s alcohol, screen exposure, inconsistent bedtimes, or sleep apnea, will blunt your overnight HRV.
Controlled breathing offers a more immediate boost. Breathing at your “resonance frequency,” typically around 4.5 to 6.5 breaths per minute for adults, can increase the amplitude of heart rate oscillations by 4 to 10 times during the session. This works by synchronizing your breathing rhythm with your body’s natural blood pressure regulation loop, maximizing the push and pull between inhalation and exhalation. A simple approach is to inhale for about 5 seconds and exhale for about 5 seconds, aiming for roughly 6 breaths per minute. Even 5 to 10 minutes of this practice has acute effects, and regular practice over weeks can raise resting HRV.
Which Metric Your Wearable Reports
Most consumer devices, including Apple Watch, WHOOP, Oura, Garmin, and Fitbit, report RMSSD or a value derived from it. RMSSD captures beat-to-beat variation and can be reliably measured in recordings as short as 10 seconds, which makes it practical for wearable use. You may also see SDNN referenced in clinical or research contexts. SDNN measures overall variability across a longer recording period and is better suited to 24-hour monitoring than the short snapshots wearables take overnight.
If your device reports HRV as a single number in milliseconds, it’s almost certainly RMSSD. Some devices apply proprietary transformations or scoring systems on top of the raw RMSSD value, so a “score” of 75 on one platform won’t mean the same thing as 75 ms on another. When comparing to the age-based ranges above, make sure you’re looking at the raw millisecond value, not a proprietary score.