Garmin shows HRV as a nightly value in milliseconds, worked out from wrist heart rate readings while you sleep, and as an HRV Status that compares your seven-day average with your own baseline Baseline Your own usual HRV level and range, built from weeks of readings taken the same way. Comparing a reading with your baseline says more than comparing it with other people. More about Baseline range. Garmin does not state outright which statistic the watch shows, and in an independent 2025 study the Garmin Fenix 6 agreed with a chest-strap ECG ECG A recording of the heart's electrical activity, taken with electrodes on the skin. ECG-based RR intervals are the reference standard for measuring HRV. More about ECG less closely than Oura or WHOOP (Dial and colleagues, 2025).
Documentation checked: 20 October 2026. Garmin updates its watches often, so details can change.
What number Garmin shows
Garmin shows a nightly HRV in milliseconds and, once it has enough data, an HRV Status. You can see both on the watch and, after a sync, in Garmin Connect, which also shows your trend (Garmin owner’s manual).
Garmin’s manual does not name the formula. Its HRV Status explainer describes RMSSD RMSSD Root mean square of successive differences: an HRV metric built from how much each heartbeat interval differs from the next, in milliseconds. It mainly reflects vagal activity. More about RMSSD as the standard measure and says the nightly value averages the whole sleep period in 5-minute windows, but it does not state outright which statistic the watch shows (Garmin). So the value cannot be matched exactly to RMSSD or SDNN SDNN The standard deviation of all NN intervals in a recording, in milliseconds. It measures overall variability, and its value depends strongly on how long the recording lasts. More about SDNN norms. The Dial study authors state that all the devices they tested report RMSSD, and they compared the Fenix 6 with RMSSD from the ECG.
When Garmin measures
The watch analyses your wrist heart rate readings while you sleep, and Garmin says to wear it while sleeping for the best results (Garmin owner’s manual). Garmin’s aim is to measure under the same circumstances from day to day, so the values can build a personal baseline (Garmin).
The numbers arrive in stages:
- After 7 nights: your 7-day average appears.
- After about three weeks: the watch has a baseline range and shows an HRV Status.
How long until my HRV baseline is reliable compares these waiting times with other devices.
How to read HRV Status
HRV Status compares your seven-day average with your own baseline range (Garmin owner’s manual):
- Balanced (green): your seven-day average is within your baseline range.
- Unbalanced (orange): your seven-day average is above or below your baseline range.
- Low (red): your seven-day average is well below your baseline range.
- Poor (no colour): your HRV values are averaging well below the normal range for your age.
- No status: not enough data for a seven-day average.
Only Poor refers to other people. The other labels compare you with yourself. Garmin lists hard training, poor sleep, stress, and changes in activity, nutrition and alcohol as things that can move your HRV, and notes that an average above your range can follow a big jump in training (Garmin). It also advises against comparing your status with someone else’s, because their baseline range will differ.
For what an orange week means in daily life, see what unbalanced HRV status means.
Scores built on Garmin’s HRV
Garmin uses the same heart data in several other features, and each one mixes it with something else:
- Stress level (0 to 100) comes from your heart rate variability while you are inactive: 0 to 25 is resting, 26 to 50 low, 51 to 75 medium and 76 to 100 high stress (Garmin owner’s manual). See is Garmin stress the same as HRV.
- Body Battery (5 to 100) analyses heart rate variability, stress level, sleep quality and activity. Garmin says food and caffeine have no effect on it.
- Training Readiness (1 to 100) uses HRV Status with last night’s sleep score, recovery time, acute load, sleep history and stress history.
A change in any of these does not always mean HRV moved. Check the millisecond value and the status first. Recovery scores explained compares them with other makers’ scores.
Some Garmin models also offer an HRV stress test on demand. It needs a Garmin chest strap: you stand still and rest for 3 minutes, and Garmin recommends doing it at about the same time and under the same conditions each day (Garmin owner’s manual). Keep those readings separate from the overnight value.
How Garmin compares with other devices
The Dial study followed 13 healthy adults for 536 nights at home, with a Polar H10 chest-strap ECG as the reference. Agreement was measured as Lin’s concordance correlation coefficient (CCC), where 1 means perfect agreement with the ECG; the authors rated 0.80 to 0.89 as poor. For overnight RMSSD the Fenix 6 scored 0.87, with an average error (MAPE) of 10.52%, against 0.99 and 5.96% for Oura Gen 4 and 0.94 and 8.17% for WHOOP 4.0. Garmin was left out of the resting heart rate Resting heart rate How many times your heart beats per minute while you are fully at rest. For adults it is usually 60 to 100 beats per minute, and lower in well-trained athletes. More about Resting heart rate analysis because of differences in method.
At an RMSSD of 50 ms, an average error of about 10% means a typical night is off by about 5 ms. That is one more reason to read Garmin’s 7-day average and status rather than single nights. The study was small, included only healthy adults and tested one older model, so newer Garmin watches may differ. The HRV by device guide has the full table.
What to watch out for
- A new watch or an update can shift your values. A step on the date of a new watch or a firmware update comes from the measurement. See can a software update change my HRV.
- Resetting does not fix a baseline. It only restarts the three-week wait. See should I reset my watch to fix my HRV baseline.
- Missing nights slow everything down. The status needs consistent sleep data.
- Keep the watch on the same wrist, at the same tightness. That keeps your nights comparable.
- Your raw beats are available. The RR converter turns a Garmin export of beat intervals into a plain RR file you can analyse yourself.