Every popular wearable records HRV, but each puts it somewhere different and calls it something different. The table below says where to look, what the number is called, and when it is measured, from each maker’s own documentation as of 14 October 2026.
Where to look
| Device | Where HRV is | What it is called | When it is measured |
|---|---|---|---|
| Oura Ring | Readiness view and Trends in the Oura app | Average HRV and Max HRV, in ms; HRV Balance as a Readiness contributor | During sleep, as 5-minute samples |
| WHOOP | The Recovery record in the app; the developer API names its field for 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 in ms | Heart rate variability, feeding Recovery | During sleep |
| Garmin | HRV Status in Garmin Connect, and on the watch, after three weeks of sleep data | HRV Status (Balanced, Unbalanced, Low, Poor) with the ms value | During sleep |
| Apple Watch | Health app, Heart section; on Series 12 and Ultra 4, Recovery HRV in the watch’s Heart Rate app | Heart Rate Variability ( 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 ); Recovery HRV | Short samples while still |
| Polar | Nightly Recharge in the Polar Flow app | HRV (RMSSD) inside the ANS Autonomic nervous system The part of the nervous system that runs the body without conscious control, including heart rate. HRV mostly reflects how it adjusts the heart from moment to moment. More about Autonomic nervous system charge | First four hours of sleep |
| Fitbit | Google Health app, Health tab, Vitals, Heart rate variability | HRV (RMSSD) | Longest sleep over three hours in the past 24 hours |
| Samsung Galaxy Watch | Vitals tile in Samsung Health on the watch | Heart rate variability | While you sleep |
| COROS | HRV graph in the COROS app; Wellness Check results on the watch | HRV (RMSSD) and a normal range after a few days | During sleep; on demand with Wellness Check |
| Suunto | HRV on the watch and in the Training Zone of the Suunto app | HRV against your normal range, as a 7-day average | During sleep |
| Ultrahuman | Recovery Score Readiness score A single number, often out of 100, that a device builds from your HRV, resting heart rate, sleep and other inputs to suggest how ready you are for the day. The weighting is not published. More about Readiness score contributors in the Ultrahuman app | HRV Form | Overnight |
The HRV by device guide explains what each of these numbers is and why they differ. Makers move menus around, so if a row is out of date, search the maker’s support site for “HRV”.
A few things to know before you look
It is usually a sleep number. Oura, Garmin, Polar, Fitbit, Samsung, Coros and Suunto all take HRV from sleep, so you get one value per night and nothing on nights you did not wear the device. Apple Watch is the exception: it takes short samples while you are still, so you may see several readings a day, and Apple’s support page says the number of measurements varies with how active you are.
Some devices make you wait. Garmin’s manual says it needs three weeks of consistent sleep data before it shows HRV Status; Polar wants three consecutive nights; COROS says a normal range appears after a few days. How long until a baseline is reliable lists the waiting times.
The statistic differs. Apple Health stores SDNN; Polar, Fitbit and COROS say RMSSD; WHOOP’s developer API names its HRV field for RMSSD; Garmin, Samsung, Suunto and Ultrahuman do not name their formula. A number from one column is not a number from another. See can I convert SDNN to RMSSD.
Scores are not HRV. Oura’s Readiness, Garmin’s Body Battery, Polar’s ANS charge and Ultrahuman’s Recovery Score mix HRV with other inputs. Look for the millisecond value behind them. Which recovery score should I trust explains why.
Taking a reading on demand
If you want a number now rather than tonight, COROS offers a Wellness Check, which it recommends taking on waking while still lying down, and some Garmin models run a three-minute HRV Stress test that needs a Garmin chest strap and asks you to stand still. A chest strap with a free app gives an ECG-quality reading any time; see how HRV is measured. Keep on-demand readings in their own series. A two-minute reading sitting up is not an overnight average, and the two should not be compared. Overnight vs morning HRV weighs the two approaches.