HRV normal ranges by age: what a typical RMSSD looks like

Why there is no single normal

Heart-rate variability is one of the most individual physiological measurements there is. In a group of healthy thirty-year-olds measured identically, resting RMSSD routinely spans a factor of four — from the high teens to the seventies — with no difference in health status between the ends. Genetics explain a large share of that spread; fitness, body composition, breathing rate during the recording and the time of day account for most of the rest.

So a “normal range” for HRV is wide by construction, and sitting in its lower half is not a finding. The table below is still useful for two things: understanding the overall shape of the age decline, and spotting a reading that falls far outside anything typical, which is a prompt to check the measurement before worrying about the physiology.

RMSSD by decade: the reference table

These figures are approximations assembled from published short-recording (5-minute, resting, supine or seated) norms in healthy adults, chiefly the Nunan review and the Shaffer & Ginsberg overview, and from the age curve reported in large cohort studies. The “typical range” is roughly the central two-thirds of readings; a reading outside it is unusual, not abnormal.

Two features of the curve matter more than any individual cell. First, the decline is steepest in the twenties and thirties and flattens later — the loss of vagal tone is front-loaded. Second, the range narrows with age in absolute terms but not in proportion: a seventy-year-old at 34 ms is as far above the median for their age as a twenty-five-year-old at 85.

Why your wearable reads higher than the lab

Most consumer devices compute RMSSD across the whole night and report an average, or the value during a particular sleep stage. Overnight, supine, in deep sleep, with slow regular breathing and no cognitive load, vagal tone is at its daily maximum. Readings taken there are commonly 20–50% higher than a seated five-minute morning recording in the same person. A forty-year-old reading 65 ms on a ring overnight is not “well above the norm” — they may be perfectly ordinary once the measurement context is matched.

The devices also differ from each other. Some average every five-minute window of the night; some use only the deepest sleep; one major brand reports SDNN rather than RMSSD from scattered daytime samples. The wearable comparison guide goes through them one by one. The practical rule: never compare a number from one device to a table built from another method.

Sex, fitness and the other modifiers

Women have slightly higher vagally mediated HRV than men through young adulthood and the gap closes after menopause; the difference is real but small relative to the between-person spread. Aerobic fitness raises resting HRV meaningfully — endurance athletes commonly sit near or above the top of their age range — though very high training loads can suppress it again. Higher body-mass index, smoking, poor sleep, and alcohol in the preceding evening all lower it. Many common medications affect it, beta-blockers most visibly.

Breathing rate during the recording is the modifier people forget. Slow breathing inflates RMSSD; a five-minute recording at six breaths a minute is not comparable to one at fourteen. If you want to compare to norms, breathe normally and do not control the breath.

How to read your own number

1. Match the method first. Seated five-minute reading against the table above; overnight wearable reading against your own device's history, not against the table.
2. Use a seven-day average, never a single day. Day-to-day variation within one person is large enough that any individual morning is close to meaningless.
3. Locate yourself roughly, then stop. “Lower third of my decade” is useful information; “38 versus a median of 41” is noise dressed as precision.
4. Track the trend against your own baseline. A sustained decline of 15–20% over several weeks, with the measurement held constant, is the signal worth acting on.

What Calmspan does with it

The optional HRV overlay in the stress test fits a smooth curve through the medians above (about 62 ms at age 20, falling roughly 1.9% per year) and asks what age your RMSSD would be typical for. That “HRV-implied age” is then blended at 45% weight with the questionnaire-based estimate. We blend rather than report it alone precisely because of everything on this page: a single number from one method is too individual to carry a verdict by itself. The full derivation is on the methodology page.