Fitbit HRV is your heart rate variability measured overnight during your longest sleep, calculated with the RMSSD formula and shown in milliseconds in the Google Health app under Health, then Vitals. There is no universal good number: Fitbit's own study of 8 million users found average morning HRV falls from around 60 ms at 25 to around 31 ms at 60, with a wide spread at every age, which is why the app compares you to your own 30-day personal range rather than a chart. This page covers where to find it, how it is measured, which devices support it, whether Premium is needed, what the published ranges say, why it drops and how it feeds the Daily Readiness Score. If you wear an Apple Watch, the metric and the maths are different; read HRV on Apple Watch explained instead.
The short version
Ignore any single night. Read the 30-day trend, and treat a sustained drop alongside a rising resting heart rate as your cue to ease off. Fitbit measures HRV once per night from sleep, using RMSSD, on every current device from the $99.95 Inspire 3 and $99.99 Fitbit Air to the Pixel Watch 5. In 2026 the metric is free; Google Health Premium buys coaching on top of it, not the number itself. Population averages exist and we print them below, but genetics and age dominate them, so a "low" reading for your age group can be perfectly healthy for you. What matters is direction against your own baseline.
Where HRV lives in the Fitbit (now Google Health) app
The Fitbit app became the Google Health app on May 19, 2026, when Google launched the Fitbit Air and folded Fitbit Premium into Google Health Premium. HRV sits where the old Health Metrics dashboard used to be. Open the app, tap the Health tab, and under Focus areas tap Vitals. Heart rate variability appears alongside breathing rate, skin temperature variation, oxygen saturation (SpO2) and resting heart rate. Tap it for daily, weekly, monthly, quarterly and yearly graphs, and tap Learn more for Google's explanation of the calculation. You can also pin HRV to the Key Metrics section on the Health tab so it shows without digging.
Alongside the number the app draws a shaded band, your personal range, calculated from up to 30 days of your own data. Inside the band is normal for you; below it is what the app treats as a meaningful dip. That band, not the raw milliseconds, is what to look at each morning.
How Fitbit measures HRV
Heart rate variability is the variation in time between consecutive heartbeats. At 60 beats a minute the gaps might run 0.96 s, 1.05 s, 0.99 s rather than exactly one second. More variation at rest generally reflects a nervous system that can shift between rest-and-digest and fight-or-flight modes; stress, illness, alcohol and heavy training suppress it. Fitbit compresses those gaps into one number using RMSSD, the root mean square of successive differences, which isolates beat-to-beat change and tracks parasympathetic activity closely. Whoop, Oura and Garmin use the same statistic, so Fitbit's readings are comparable in kind, though not in exact value.
The sampling rule matters. Google's help pages say the latest HRV reading comes from your longest sleep period in the past 24 hours, and only sleep periods longer than three hours count. So there is no daytime HRV on Fitbit and no on-demand reading: one value per night, from the most repeatable conditions your body offers.
Which Fitbit and Pixel devices track HRV
| Device | US list price | HRV in Google Health | Other Vitals supported |
|---|---|---|---|
| Fitbit Air (screenless, 2026) | $99.99 | Yes | Breathing rate, SpO2, skin temp, RHR, AFib alerts |
| Fitbit Inspire 3 | $99.95 | Yes | Breathing rate, SpO2, skin temp, RHR |
| Fitbit Charge 6 | $159.95 | Yes | All Vitals plus ECG app |
| Fitbit Versa 4 | $199.95 | Yes | Breathing rate, SpO2, skin temp, RHR |
| Fitbit Sense 2 | $249.95 | Yes | All Vitals plus ECG and EDA stress sensor |
| Pixel Watch 4 / Pixel Watch 5 | $349.99 / from $399 | Yes | All Vitals plus ECG |
| Fitbit Ace LTE (kids) | $179.99 | No | Activity only, by design |
Google's compatibility table also lists older hardware including the Charge 5, Inspire 2, Luxe and earlier Sense and Versa models. If HRV shows no data, the device does not support it or you have not yet slept a full night wearing it. Which model is worth buying at each price is covered in the cheapest Fitbit in 2026 and our Fitbit Air guide.
Does Fitbit HRV need Premium?
Not in 2026. When Fitbit launched the Health Metrics dashboard in 2020, longer trend history was a Premium perk and free users saw a shorter window. Today Google's plan comparison places HRV, breathing rate, SpO2, skin temperature, resting heart rate, sleep stages and the Daily Readiness Score under the free Base tier for anyone with a compatible device. Google Health Premium, at $9.99 a month or $99.99 a year (£8.99 or £89.99 in the UK), adds the Gemini-based Google Health Coach, adaptive fitness plans, deeper sleep insights and a workout library. It interprets your HRV; it does not unlock it. Fitbit Air buyers get a three-month Premium trial; letting it lapse does not remove the metric.
What is a good HRV on Fitbit? The published ranges
The most useful reference is Fitbit's own research. A 2020 study by Fitbit scientists analysed heart rate variability in roughly 8 million users over a single 24-hour period and published RMSSD benchmarks by age, sex and time of day. The 6 am to 7 am readings below are the closest published proxy for what you see after a night's sleep. Values are means in milliseconds, with the 25th to 75th percentile range in brackets.
| Age | Women, mean RMSSD (middle 50%) | Men, mean RMSSD (middle 50%) |
|---|---|---|
| 20 | 66 ms (37 to 85) | 74 ms (45 to 96) |
| 25 | 57 ms (32 to 73) | 61 ms (35 to 79) |
| 30 | 53 ms (31 to 67) | 56 ms (34 to 71) |
| 35 | 47 ms (29 to 60) | 49 ms (31 to 62) |
| 40 | 42 ms (26 to 52) | 43 ms (27 to 54) |
| 45 | 37 ms (24 to 46) | 38 ms (25 to 48) |
| 50 | 34 ms (22 to 42) | 34 ms (23 to 42) |
| 55 | 33 ms (22 to 40) | 32 ms (21 to 39) |
| 60 | 31 ms (21 to 38) | 31 ms (20 to 37) |
Three things stand out. HRV falls fastest between 20 and 40, then flattens. Men read slightly higher than women until about 50, after which the difference disappears. And the spread is enormous: at age 30 the middle half of men span 34 to 71 ms, so two healthy people the same age can differ by a factor of two. The study also found a dose-dependent link between daily steps and HRV, strongest in people in their twenties. Treat the table as context, not a target. Twin studies put a large share of between-person HRV difference down to genetics, which no training plan changes.
Why your Fitbit HRV is low, or suddenly dropped
If the question is "why is my Fitbit HRV low tonight", the usual suspects, in rough order of how often they show up, are: alcohol, which reliably lowers the next night's RMSSD, often visibly after just two drinks; a late or very hard workout, since the body is still in recovery when the measurement window opens; an oncoming illness, often visible a day before symptoms, which is why Google pairs HRV with skin temperature and breathing rate in the same Vitals view; short or fragmented sleep; dehydration or a late heavy meal; and stress, including travel and jet lag. Women commonly see HRV dip in the luteal phase of the menstrual cycle; a monthly pattern is normal.
If the question is "why is my Fitbit HRV always low", the answer is usually age and genetics, and the honest response is that a stable 28 ms with a steady resting heart rate is not a problem to solve. The readings that deserve attention are the ones that fall below your personal range for several nights while resting heart rate climbs. That combination is the wearable's most reliable early signal of overreaching or illness, and our recovery score explainer covers how each company turns it into a verdict.
How to use the 30-day trend instead of the daily number
Night-to-night HRV noise is large enough that a 15 percent swing means nothing on its own. The Google Health app draws your personal range from up to 30 days of data; the discipline is to look at that band rather than the headline figure. A workable routine: check the weekly view once a week, note whether the line sits inside, above or below the shaded range, and only change behaviour when three or more consecutive nights fall below it. Wear the device every night, keep bedtime roughly consistent, and stick with one device, because a Charge 6 and a Pixel Watch on alternate nights will not produce a clean series.
Two things not to do. Do not compare your number with a friend's Whoop, Oura or Apple Watch reading; different statistics and sampling windows produce different values. And do not chase a higher HRV as a goal in itself. Consistent sleep, less alcohol and sensible training load move it as a by-product; forcing it produces anxiety about a number that was never meant to be graded.
How HRV feeds the Daily Readiness Score
Fitbit's Daily Readiness Score, free in the Base tier since Google's 2026 plan restructure, is where HRV does its practical work. The score, from 1 to 100, combines three inputs: your recent activity (fitness fatigue), last night's sleep, and HRV relative to your baseline. A high score means the app thinks you have capacity for a hard session; a low score comes with a suggestion to prioritise rest or a light walk. Because HRV is one of the three legs, a low-HRV night pulls readiness down even when sleep duration looked fine, the situation where the wearable knows something you do not yet feel.
The same overnight data reaches other apps through Health Connect on Android or Apple Health on iPhone. Fitcoin, our own app, reads those platforms to turn your workouts into a daily FitScore, weekly Leagues and partner rewards, and uses the same sleep and heart data for its Recovery and Energy insights. For how rival systems frame the same physiology, see the best HRV apps for Apple Watch and the Whoop Recovery score explainer. If steps from another source are not reaching Fitbit, how to add steps to Fitbit fixes the plumbing.
Frequently asked questions
What is a good HRV on Fitbit?
There is no single good number. In Fitbit's own study of 8 million users, average morning RMSSD ran from about 60 ms at age 25 to about 31 ms at age 60, with the middle half of people at any age spread across a 25 to 30 ms band. A 28 ms reading can be normal for a healthy 55-year-old and a warning sign for a 25-year-old. Judge your HRV against your own 30-day personal range in the Google Health app, not against a chart.
Why is my Fitbit HRV so low?
A one-night drop usually traces to alcohol, a late or very hard workout, an oncoming illness, poor or short sleep, dehydration, or a late heavy meal. A sustained low reading over weeks is more often genetics and age than a health problem. Check that you wore the device for at least three hours of sleep, since Fitbit skips shorter sleeps, and compare against your 30-day range before reacting.
Does Fitbit HRV require Premium?
No, not in 2026. Google lists HRV, breathing rate, SpO2, skin temperature and resting heart rate under the free Base tier of the Google Health app, alongside the Daily Readiness Score. Google Health Premium ($9.99 a month or $99.99 a year) adds the Gemini-based Health Coach and deeper sleep insights, not the HRV metric itself. Longer trend history was a Premium perk when the Health Metrics dashboard launched in 2020.
Why is my Fitbit HRV different from my Apple Watch or Whoop HRV?
Fitbit and Whoop both report RMSSD, but Fitbit takes it from your longest sleep period while Whoop weights deep sleep, so the numbers differ. Apple Watch reports SDNN, a different statistic taken at scattered moments through the day, and its values are usually higher and noisier. Never compare HRV across brands; only compare a device with its own history.
Method: Checked September 8, 2026 using Google Health help pages on heart rate and vitals tracking, the Google Store's Fitbit and Pixel Watch listings, Google's Health Premium plan comparison, and the 2020 Fitbit study of heart rate variability in 8 million users. Population figures are 6 am to 7 am RMSSD means from that study and are a proxy for overnight values, not Fitbit's exact sleep calculation. Prices are US list at publication and change often. Fitcoin has no commercial relationship with Google, Fitbit, Apple, Whoop or any hardware brand named here. Wellness estimates only, not medical advice.
About the author: Harris Khan is the co-founder and CTO of Fitcoin, a UK fitness-rewards app.