What Is a Good HRV for Your Age? The Honest Answer Is That Nobody Can Tell You

You want a number. Something of the form "a good HRV for a 40-year-old is this many milliseconds", so you can check yours against it and find out whether you are healthy.

That number does not exist, and this is the one page on the topic that will tell you so rather than invent one.

It is not that HRV is useless — it is one of the more informative things a watch can measure. The problem is narrower than "individual variation is high", although that is also true. The charts circulating online are comparing numbers that are not measurements of the same thing. Put a chest strap and a wrist watch on the same person on the same night and they will not agree. Compare a morning reading to an overnight average and they will not agree either. Averaging all that into a tidy table by decade produces something that looks authoritative and means very little.

First, what HRV actually is

Your heart does not beat like a metronome. Even at complete rest, the gap between one beat and the next varies slightly — a little shorter as you breathe in, a little longer as you breathe out. Heart rate variability measures that wobble.

It matters because of what causes it: the balance between the two halves of your autonomic nervous system, the sympathetic side (stress, effort, adrenaline) and the parasympathetic side (rest, recovery, digestion). More variability generally means the parasympathetic side has the upper hand, which is what you want at rest.

rMSSD, in plain English

You will see "rMSSD" attached to HRV numbers, and it is worth 30 seconds because it explains much of the confusion.

rMSSD stands for the root mean square of successive differences. Unpack it backwards:

• Successive differences: take the gap between beat one and beat two, then beat two and beat three, and so on — then look at how much each gap differs from the one before.
• Root mean square: a standard way of averaging those differences so the big ones count for more and positives do not cancel negatives.

So rMSSD is roughly "the typical size of the beat-to-beat change", in milliseconds. It is the most common HRV metric on consumer wearables because it is reliable over short recordings and tracks the parasympathetic side closely.

The critical consequence: rMSSD is built entirely from the timing of individual heartbeats. How good your number is depends on how precisely your device knows when each beat happened — and that is where devices diverge.

Why the numbers aren't comparable across devices

There are three broad ways HRV gets measured, and they are not equivalent:

Method	How it detects beats	Practical accuracy
Chest strap	Electrical signal from the heart itself, like a simplified ECG	The reference standard for consumer HRV. Sharp, unambiguous beat timing.
Wrist watch or ring (optical)	Shines light into the skin and watches the blood-flow pulse	Good at rest and overnight. Degrades with movement, cold hands, loose fit.
Phone camera app	Fingertip pulse read through the phone's lens	Workable for a still, seated reading. Very sensitive to technique.

An electrical signal gives a crisp spike you can time precisely. An optical sensor infers the beat from a smooth pressure wave arriving at your wrist — a blurrier event, and unevenly blurry. Small timing errors do not average out; they change the answer.

Hence the most useful rule in consumer HRV: never compare your HRV to a number from a different device or method. Not your training partner's ring, not a chart on another app's blog, not your own chest-strap figure from two years ago.

And why they aren't comparable across conditions either

Even on one device, the number moves with the circumstances:

• Time of day. HRV follows a daily rhythm. An overnight average, a waking reading and a 4pm reading are three different quantities.
• Overnight average versus spot reading. Most watches average across your whole sleep; a morning app reading is a 60-second snapshot. The overnight figure is usually steadier.
• Breathing rate. Large and under-appreciated. A big chunk of beat-to-beat variation is driven by your breath, so breathing slowly and deeply during a measurement raises the number. Any guided-breathing protocol is partly measuring your breathing.
• Position, and whether you just moved. Lying, sitting and standing all give different values.

Stack the device differences on the condition differences and you can see what those age-band tables are: measurements taken under conditions that were never standardised, presented as a reference range.

What does drive real differences between people

Genuine physiological differences exist — they are just enormous and overlapping. What matters most:

• Genetics. The biggest single factor, and the one you cannot do anything about. Two healthy, equally fit people of the same age can sit a long way apart.
• Age. HRV does tend to decline across adult life, on average, in populations. The trend is real; the spread around it is so wide that someone's age tells you remarkably little about their expected value.
• Fitness, especially endurance training. Trained endurance athletes do tend to sit higher than untrained people of the same age, consistent with how aerobic training strengthens parasympathetic tone.
• Resting heart rate. The two are related — a lower resting heart rate leaves more room for variation between beats — which is part of why fitter people tend to read higher.
• Health conditions and medications. A long list of both affect HRV, which is one reason a wearable number is not a health screen.

Notice what this does not support: a lookup table. If genetics is the dominant term, an age band cannot tell you whether your value is good — only what a population average looked like, which is not what you asked.

What to do instead: build your own baseline

This limitation is not a dead end. Your HRV needs comparing to your own recent history, not to anyone else. A change in your own number, measured the same way each time, is real information. The absolute value is not.

How to establish one that means something:

1. Pick one method and never change it. Overnight from a watch, or a strap reading in the same position every morning. Switching methods restarts the baseline — you have changed the instrument.
2. Be consistent about conditions. Same time, same posture, same breathing. Overnight measurement does this for you, which is its main advantage.
3. Collect weeks, not days. Expect around three to four weeks of near-daily data before a baseline is stable enough to judge against. Garmin's HRV Status will not display until it has three weeks of consistent sleep data, which is a fair guide to the order of magnitude.
4. Then watch the trend, not the day. A weekly average against your established band tells you something. A single night is mostly noise.

What counts as a meaningful deviation

You work this out from your own spread, not from a rule. After several weeks you can see how much your value bounces around on ordinary days — that scatter is your noise floor. A day inside it is not news. A week clearly outside it is.

There is no percentage worth printing here, and that is not evasion: a meaningful deviation for someone with a tight spread is much smaller than for someone whose nightly values swing widely, so any single rule would be wrong for one of them. If you use a Garmin, this is exactly the work the HRV Status baseline band does for you — we have explained how it works and how it is commonly misread separately.

The things that reliably move your HRV

Short, well-supported, and much the same for everyone. In rough order of how dependably they show up:

• Alcohol. The most consistent single-night suppressor here. An evening's drinking shows clearly on that night's reading, often into the next.
• Illness. HRV often falls as an infection takes hold, sometimes before you feel symptoms.
• Poor or short sleep. Duration and disruption both matter.
• Hard training. A demanding session suppresses overnight HRV for a night or two — the expected response to training stress, not a sign you overdid it.
• Heat. A hot bedroom, a late sauna, or training in the heat all push it down.
• Breathing rate. Slower breathing raises the reading. Mostly relevant to spot measurements, where it can masquerade as recovery.
• Late heavy meals, stress and travel. Less reliable individually, but worth noting when you are hunting for an explanation.

Notice how ordinary that list is. Most "unexplained" HRV drops have an explanation sitting in plain sight from the previous evening.

When a number does deserve attention

This is not medical advice, and a wearable is not a diagnostic device. HRV is affected by many medical conditions and medications, and a low number has far too many possible causes for anyone to interpret it for you from a blog post.

The pattern worth taking to a professional rather than the internet is a sustained fall in your own baseline with no obvious explanation — no hard block, no illness you noticed, no bad sleep — especially alongside an unexplained rise in resting heart rate, fatigue that does not lift with rest, breathlessness or chest discomfort. If it comes with the usual signs of overtraining, change the training first and call a doctor if it does not resolve.

Why "by age" is such a popular question — and a familiar mistake

This is the second time age has been offered to endurance athletes as a substitute for measurement.

The first was maximum heart rate. "220 minus your age" has been handed out for decades as if it described an individual, when it is a rough line through a cloud of other people's data — which is why your watch's max heart rate is probably wrong, and why that one bad number corrupts five others. Age-based heart rate zone calculations have the same shape: a reasonable start when you have nothing else, a poor substitute once you do.

An HRV-by-age table is the same error wearing newer clothes. Age gets used because it is the only variable the author knows about you.

So what should you actually track?

Your own HRV trend — same device, same conditions, judged weekly — cross-checked against how you feel and what you can do in a session. That last one is the outcome the other two are proxies for.

HRV earns its place as an early-warning signal for accumulated fatigue and illness. It does not earn a place as a score. And the gap between "here is a trend" and "here is what to do about it on Tuesday" is the part your watch does not do — it hands you a graph and leaves the interpretation to you. Joining that trend to your training history and changing the plan accordingly is what Lactate Training is for: it reads the data your Garmin already collects and adapts the week around it.

If you want the broader map of which of your watch's numbers are measured, which are estimated and which are guesses, start with what every Garmin metric actually means.

Frequently asked questions

What is a good HRV for a 40-year-old?

There is no defensible single answer, and any chart giving you one is comparing readings from different devices taken under different conditions. Genetics is the largest driver of HRV differences between people, so two healthy 40-year-olds can sit a long way apart. Compare against your own baseline instead, built from three to four weeks of consistent measurement on one device.

Why is my HRV lower than my friend's?

Most likely because you are not measuring the same thing. Different devices and methods — chest strap, wrist optical, phone camera — produce different numbers for the same person, as do overnight averages versus morning spot readings. Beyond that, genetics accounts for much of the real difference. Neither of you learns anything from the comparison.

What does rMSSD mean?

rMSSD is the root mean square of successive differences: it looks at how much each beat-to-beat gap differs from the one before, averaged into a single figure in milliseconds. It is the most common HRV metric on consumer wearables because it works well over short recordings and closely tracks the parasympathetic nervous system.

Does HRV go down with age?

On average, across populations, yes — HRV tends to decline across adult life. But the spread around that trend is very wide, so your age tells you little about what your value should be. The trend is real at population level and close to useless at individual level.

How long does it take to establish an HRV baseline?

Expect around three to four weeks of near-daily measurement on the same device under the same conditions. As a reference point, Garmin's HRV Status will not display at all until the watch has three weeks of consistent overnight sleep data.

Do endurance athletes have higher HRV?

They tend to, compared with untrained people of similar age, which fits how aerobic training strengthens parasympathetic tone and lowers resting heart rate. It is a tendency rather than a rule, and not reliable enough to use as a fitness test — plenty of very fit people read lower than less fit ones.

Your own baseline is the only table that matters

The single HRV number worth training off is your own trend. Lactate Training reads the Garmin health data you already collect and adapts your week around it, so the trend changes what you do rather than what you worry about.

See what it does with your data →