You can download your HRV from almost every wearable, but the file holds one of three things: every interval between your heartbeats, one HRV value per reading, or one number per night. Only the first lets you work out HRV yourself; the other two are numbers the device has already calculated.
This guide gives the export steps for each platform, says which of the three you get and in what format, and ends with what you can do with the file. Makers’ help pages and developer documentation checked on 22 October 2026. Apps change their menus, so if a step does not match yours, follow the maker’s page in the sources.
The three depths of HRV data
One night at three depths
Made-up data from a teaching model
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Beat to beat (RR intervals)
Every interval between heartbeats, about 60 to 80 a minute at rest.
Work out RMSSD, SDNN, frequency measures or any other, and check the beats for artifacts yourself.
For example: Apple Health’s export.xml, a Garmin activity with Log HRV on, a Polar Flow RR file, chest-strap apps.
RMSSD of this minute: 33 ms
Lost: the beats themselves. No other measure can be worked out.
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Per reading
One HRV value per reading or per few minutes, already worked out by the device.
See how HRV moved through the night. The measure is the maker’s, and it cannot be worked out again.
For example: Apple Watch SDNN readings; Oura’s 5-minute samples; Polar’s through its API.
90 values, one per 5 minutes asleep
Lost: when in the night each value came from.
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Nightly summary
One number per night or day: the one the app shows.
Follow your trend over weeks, against your own earlier nights from the same device.
For example: WHOOP’s and Oura’s CSV exports; Polar’s Nightly Recharge through its API.
Last night: 47.5 ms, the mean of the values above
Three panels, one under the other. First, beat to beat: a bar chart of 69 intervals between heartbeats over one minute, whose RMSSD is 33 ms. Second, per reading: 90 dots, one HRV value for every 5 minutes of sleep through the night. Third, nightly summary: 14 bars, one per night; the last bar, 47.5 ms, is the mean of the dots above it. Between the panels, notes say what is lost: first the beats themselves, then when in the night each value came from.
Beat to beat. An RR interval RR interval The time from one heartbeat to the next, measured in milliseconds between the R peaks of an ECG. HRV is calculated from a series of these intervals. More about RR interval is the time between two heartbeats, in milliseconds. A file of them holds the raw material of every HRV measure: 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 , 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 and the frequency measures are all calculated from these intervals (Task Force, 1996). With the beats you choose the measure and the time window, you decide how extra beats and dropouts are cleaned out, and you can compare two devices on the same terms.
Per reading. Each row is an HRV value the device already worked out, such as an Apple Watch SDNN reading or a ring’s 5-minute RMSSD sample. You can see how HRV moved through a night, but not recompute it, and you keep the maker’s statistic. SDNN and RMSSD measure different things, so one cannot be turned into the other (can I convert SDNN to RMSSD?).
Nightly summary. One number per night or day, usually the one the app shows. That is enough to follow your trend in a spreadsheet, as long as you compare each night only with earlier nights from the same device.
Many exports hold more than one depth. Apple’s file has the readings and, inside them, the beats; Polar’s developer API gives a 4-hour nightly average and 5-minute HRV samples.
What each platform’s export holds
What each export holds
From the makers’ pages, 22 October 2026
| Platform | Beats | Readings | Nightly | Files | RR converter |
|---|---|---|---|---|---|
| Apple Health Each Apple Watch HRV reading (SDNN) lists the time of every beat it used. | In the export | In the export | Not in the export | XML | Reads it |
| Garmin Connect Beats in an activity’s FIT file with Log HRV on. Daily wellness files include HRV, at a level Garmin does not state. | Only with a setting or sensor | Not stated by the maker | Not stated by the maker | FIT, CSV | If it holds beats |
| Oura Nightly HRV and its 5-minute samples, in the data models of Oura’s API, which the export follows. The API needs a membership. | Not in the export | In the export | In the export | CSV, JSON | Tells you: no beats |
| WHOOP One HRV value per cycle, from one sleep to the next, in the Physiological Cycles file. | Not in the export | Not in the export | In the export | CSV | Tells you: no beats |
| Polar Flow RR file for watch sessions recorded with a Polar ECG strap; Nightly Recharge values through the API. | Only with a setting or sensor | Through the developer API | Through the developer API | CSV, FIT, TCX, JSON | If it holds beats |
| Google Health (Fitbit) Takeout: Google gives activity, exercise, sleep and heart rate as examples, not HRV. Daily and sample HRV through the API. | Not in the export | Through the developer API | Through the developer API | Takeout | Tells you: no beats |
| Samsung Health Download personal data; Samsung does not list the files. | Not stated by the maker | Not stated by the maker | Not stated by the maker | Not stated | Can’t open it |
| COROS Activities as FIT or TCX. Daily and sleep data by request; HRV not named. | Not stated by the maker | Not stated by the maker | Not stated by the maker | FIT, TCX | If it holds beats |
| Suunto A workout as FIT or GPX; beat intervals not mentioned. | Not stated by the maker | Not stated by the maker | Not stated by the maker | FIT, GPX | If it holds beats |
| Withings CSV export; HRV is not on the list. HRV can go to Apple Health. | Not in the export | Not in the export | Not in the export | CSV | Can’t open it |
| Elite HRV · Welltory · Polar Sensor Logger Their RR exports: one file of beats per reading or time range. | In the export | Not in the export | Not in the export | TXT, CSV | Reads it |
A table of platforms against three depths of HRV data: beats, readings and nightly values. Apple Health: beats, In the export; readings, In the export; nightly, Not in the export. Files: XML. RR converter: Reads it. Each Apple Watch HRV reading (SDNN) lists the time of every beat it used. Garmin Connect: beats, Only with a setting or sensor; readings, Not stated by the maker; nightly, Not stated by the maker. Files: FIT, CSV. RR converter: If it holds beats. Beats in an activity’s FIT file with Log HRV on. Daily wellness files include HRV, at a level Garmin does not state. Oura: beats, Not in the export; readings, In the export; nightly, In the export. Files: CSV, JSON. RR converter: Tells you: no beats. Nightly HRV and its 5-minute samples, in the data models of Oura’s API, which the export follows. The API needs a membership. WHOOP: beats, Not in the export; readings, Not in the export; nightly, In the export. Files: CSV. RR converter: Tells you: no beats. One HRV value per cycle, from one sleep to the next, in the Physiological Cycles file. Polar Flow: beats, Only with a setting or sensor; readings, Through the developer API; nightly, Through the developer API. Files: CSV, FIT, TCX, JSON. RR converter: If it holds beats. RR file for watch sessions recorded with a Polar ECG strap; Nightly Recharge values through the API. Google Health (Fitbit): beats, Not in the export; readings, Through the developer API; nightly, Through the developer API. Files: Takeout. RR converter: Tells you: no beats. Takeout: Google gives activity, exercise, sleep and heart rate as examples, not HRV. Daily and sample HRV through the API. Samsung Health: beats, Not stated by the maker; readings, Not stated by the maker; nightly, Not stated by the maker. Files: Not stated. RR converter: Can’t open it. Download personal data; Samsung does not list the files. COROS: beats, Not stated by the maker; readings, Not stated by the maker; nightly, Not stated by the maker. Files: FIT, TCX. RR converter: If it holds beats. Activities as FIT or TCX. Daily and sleep data by request; HRV not named. Suunto: beats, Not stated by the maker; readings, Not stated by the maker; nightly, Not stated by the maker. Files: FIT, GPX. RR converter: If it holds beats. A workout as FIT or GPX; beat intervals not mentioned. Withings: beats, Not in the export; readings, Not in the export; nightly, Not in the export. Files: CSV. RR converter: Can’t open it. CSV export; HRV is not on the list. HRV can go to Apple Health. Elite HRV · Welltory · Polar Sensor Logger: beats, In the export; readings, Not in the export; nightly, Not in the export. Files: TXT, CSV. RR converter: Reads it. Their RR exports: one file of beats per reading or time range.
The sections below give the steps and the source for every cell. The last column says what this site’s RR converter does with the file; more on that under what to do with your HRV export.
How to export HRV from Apple Health
On iPhone, open the Health app, tap Summary, then your picture or initials, then Export All Health Data, and choose how to share the file (Apple, iPhone User Guide). Apple exports all your health and fitness data in XML. If what you saved is a ZIP archive, unzip it: the file you need is export.xml.
What the file holds:
- Readings. HealthKit, the health database on iPhone, stores Apple Watch HRV as SDNN, the standard deviation of the intervals between normal beats, and “the system automatically records samples on Apple Watch” (Apple, HealthKit). Each reading is one record with its time and value in ms.
- Beats. Apple does not publish the layout of
export.xml. In the exports we have read, each Apple Watch HRV record also lists the time of every beat in that reading, as entries namedInstantaneousBeatsPerMinute. The gaps between those times are the RR intervals. HealthKit also has a heartbeat series type, which keeps the time of each beat and flags a gap where beats may be missing (Apple, HealthKit); the converter reads these records too when an export has them. - No nightly value. HealthKit’s quantity types for HRV are SDNN and, newer, RMSSD; it has no daily HRV type (Apple, HealthKit). Other apps can write HRV into Health as well, so check which app each record came from before you put values side by side.
Apple Watch HRV explains when the watch takes its readings and why the numbers run lower than other devices’.
How to export HRV data from Garmin Connect
Garmin keeps HRV in two different places, and each has its own export (Garmin Support):
- Beats, from an activity. On the Garmin Connect website, select Activities, then All Activities, open the activity, select the gear icon and choose Export File. Garmin says the file comes “in the original file format from the device, typically a .fit file”. It holds beat intervals only if the watch was logging them: the Log HRV setting “enables the watch to record your heart rate variability during an activity” (Garmin, fēnix E owner’s manual). On the fēnix E it is under Watch Settings, System, Advanced, Data Recording; on Edge bike computers under System, Data Recording (Garmin, Edge 1030 owner’s manual). The menu differs by model, so search your manual for “Log HRV”, and turn it on before the activity you want to record.
- Overnight HRV, from wellness files. On the website, select your profile icon, Account Settings, Account information, pick a date at the bottom of the screen and select Export. You get that day’s wellness files as original FIT files in a ZIP, which Garmin says include “steps, sleep, stress, HRV and more”. Garmin does not say whether the HRV in them is the overnight value, the readings behind it, or both.
- Your whole account. From Garmin Account Data Management, select Export Your Data, then Request Data Export. Garmin emails a download link, “typically” within 48 hours, though it can take up to 30 days. Your activities are inside, as FIT files, in the
DI_CONNECTfolder.
Reports and the activity list also export as CSV, as summaries for a spreadsheet; Garmin’s page does not mention HRV for either. Garmin HRV covers what the overnight number is and how HRV Status uses it.
How to export Oura data (CSV and API)
The CSV export. Log in to the Membership Hub, select Export data, then Request your data. It can take up to 10 days; Oura emails you when the export is ready, and you download it from the Membership Hub. This works with or without an active membership, and the files are CSV (Oura Member Care). Oura says their data models are described in its API documentation, and that durations in the files are in seconds, not hours and minutes (Oura Member Care).
The API. Oura’s API needs an active membership (Oura Member Care, membership). Since personal access tokens were withdrawn in December 2025, it is reached through an app that signs in to your account (Oura API). For each sleep its data model holds the average HRV and an object of HRV samples with the interval between them (Oura API). Oura’s help page says the nightly value is “the mean of all five-minute samples taken while you sleep” (Oura Member Care, HRV).
Neither route gives beats. No data model in Oura’s API documentation holds beat-to-beat intervals. Oura HRV covers what the nightly number measures.
How to export WHOOP data
In the WHOOP app, tap the More icon in the navigation bar, then Data Export (on iPhone, App Settings first), confirm your email address and select Create Export. WHOOP emails a link within 24 hours, and the link expires after 7 days (WHOOP Support).
You get several CSV files. Physiological Cycles holds Recovery, 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 and HRV for each cycle, along with strain, sleep times and more; Sleeps, Workouts and Journal Entries hold the rest. WHOOP’s developer API gives each Recovery with its HRV as RMSSD in milliseconds (WHOOP for Developers). Neither holds beat intervals. WHOOP HRV explains which part of the night the value comes from.
How to export RR intervals from Polar Flow
Polar documents an export of RR intervals, and three other routes:
- RR intervals of a training session. “Training sessions recorded with an 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 heart rate sensor include downloadable RR interval data”, which you export as CSV from the session’s Training analysis page on the Flow website (Polar Support, RR data export). Polar lists watches from the Ignite, Pacer, Unite, Vantage, Grit X and Street X lines, and the H10 and H9 straps. There is no RR file when the session was recorded in the Polar Flow or Beat app, even with an ECG strap, when it was recorded to the H10’s own memory and processed in Beat, or when an optical sensor gave the heart rate.
- A session’s files. On the Flow website, open the session from the Diary and use the Export menu at the top right for TCX, CSV, FIT or GPX, or a ZIP of them (Polar Support, session export). Polar lists heart rate, calorie and cadence data for these files, not RR intervals.
- Everything in your account. At account.polar.com, select Download your data. Polar emails you when it is ready, and you then have two weeks to download it. Polar says it leaves out anything its algorithms derive from your data, naming activity and sleep information as examples (Polar Support, download all your data).
- The AccessLink API. Any registered Polar Flow user can create an API client. For each night it gives the RMSSD averaged over 4 hours, starting 30 minutes after you fall asleep, and 5-minute HRV samples. For a training session done with an H6, H7, H9 or H10 strap, it gives RR interval samples, but only for sessions uploaded in the last 30 days and after you linked the client to your account (Polar AccessLink).
An H10 used without a Polar watch sends heart rate and RR intervals to whatever app it is paired with. Polar’s SDK documentation lists heart rate once a second, and no RR intervals, for recordings to the H10’s own memory (Polar, H10 SDK), so to keep the beats, use an app that saves them, such as those in chest-strap apps. Polar HRV covers Nightly Recharge and the Orthostatic test Orthostatic test A short morning test: lie or sit still for 2 minutes, then stand for 2 minutes, recording heart rate and HRV in both positions to see how your body handles standing up. More about Orthostatic test .
How to export Fitbit and Google Health data
Fitbit accounts now live in Google accounts. Since 19 May 2026 you can no longer use Fitbit with a Fitbit login. For accounts that were not moved, Google set 15 July 2026 as the day it would begin processing data deletions; its page does not say what has been deleted since (Google Health Help, moving your account).
To export, use Google’s download of your Google data, Google Takeout, with Google Health selected (Google Health Help, export). Google’s export page gives “activity, exercise, sleep, and heart rate” as examples and does not mention HRV. GPS workouts can also be exported one at a time as TCX files from the Google Health app’s Fitness tab.
For apps, the Google Health API has a daily HRV type and an HRV sample type, both RMSSD in milliseconds (Google for Developers, vitals). Its list of data types has no beat-to-beat intervals (Google for Developers, data types). The older Fitbit Web API gave the night’s RMSSD and 5-minute values; the Fitbit developer site says it “will be turned off” on 30 October 2026, and the Google Health API reference gives 2 November 2026 (Fitbit Developer; Google for Developers, Health API reference). Fitbit and Pixel Watch HRV explains which sleep the value comes from.
Samsung Health, COROS, Suunto and Withings
Samsung Health
In Samsung Health, tap More options (the three dots), Settings, then Download personal data and Download, and sign in to your Samsung account. The files land in My Files, under Downloads, in a Samsung Health folder (Samsung Support). Samsung does not list which files you get or whether HRV is among them. See Galaxy Watch HRV and Galaxy Ring HRV for what the devices measure.
COROS
Workouts export in bulk from the Training Hub on a computer: open the Activity List, select Export Data, choose FIT or TCX and give an email address. Sleep and daily data come by request: in the COROS app, go to the Profile page, Customer Support, Contact Support, and give the date range you want (COROS Help Center). COROS names daily metrics, sleep and heart rate for that route, not HRV, and does not say whether its FIT files carry beat intervals. More in COROS HRV.
Suunto
In the Suunto app, open a workout, tap the three dots at the top right and choose FIT or GPX. Suunto says a FIT file holds “location, time, timestamps, heart rate, power, cadence, etc.” (Suunto Support). It does not mention beat intervals or the nightly HRV. More in Suunto HRV.
Withings
In the Withings app, go to your profile, tap the settings icon, then Export All Health Data, choose your user profile and tap Start my archive; a CSV file arrives by email (Withings Support, exporting your data). HRV is not on Withings’ list of exported data. It is on the list of data Withings shares with Apple Health, and accounts opened on or after 13 October 2026 need a Withings+ subscription to send data to Apple Health or Health Connect (Withings Support, Apple Health). More in Withings HRV.
Rings and watches that keep HRV in the app
For some devices we found no file export of HRV in the maker’s pages. On an iPhone, Apple Health can be the way out:
- Ultrahuman writes HRV to Apple Health when the integration is on (Ultrahuman Blog). Its developer documentation also offers a personal API token that reads your own account’s daily metrics, HRV among them, up to 7 days per request: a route for programmers, not a download (Ultrahuman, UltraSignal API).
- Amazfit added “support for syncing HRV data to Apple Health” to the Balance 3 in its July 2026 update OTA 3 (Amazfit, Balance 3).
- RingConn says HRV does not sync to Health Connect “because of an algorithm compatibility issue” (RingConn).
Values that reach Apple Health this way are readings, and their export holds the values the app wrote, not beats. Ultrahuman and Amazfit do not say which statistic they write, so keep them apart from Apple Watch’s SDNN. See Ultrahuman, Amazfit and RingConn.
Chest-strap apps that export RR intervals
A chest strap such as the Polar H10 sends RR intervals over Bluetooth, and several apps save them to a file:
- Elite HRV. In the app’s settings (top right), the data export sits below “Set reading reminders”. Elite HRV emails a private link that expires after a few hours. The download holds every reading you have taken, one text file per reading, named by its date and time, with one RR interval per line. Only the reading’s start time is given, not a time for each beat (Elite HRV Knowledge Base).
- Welltory. Sign in to the Welltory web app, open Dashboard, pick a chart and a time range, and choose Download raw RR-intervals (Welltory Help Center).
- Polar Sensor Logger. An Android app that saves heart rate, RR intervals and ECG from an H10 (heart rate and RR from an H7 or H9) to files on the phone, which you can share by email or to Google Drive. Its developer states it is not an official Polar app (Google Play).
The RR converter also reads RR text files written for Kubios HRV. We found no RR export documented by HRV4Training, so no steps are given for it here. Chest-strap HRV covers getting a clean recording in the first place.
No export button? Ask for a copy
If a service has no export, or its export leaves out data you want, you can ask the company for a copy of your personal data under data-protection law. In the EU, the right of access entitles you to a copy, the first one free of charge (European Commission); in the UK, an organisation usually has one month to answer a subject access request (ICO). The guide Wearable data rights: how to get a full copy explains what to ask for and how, and the tool Data request letter builds the letter from your answers.
What to do with your HRV export
A file with beats: the RR converter and the HRV Analyzer
The RR converter turns an export into a plain list of RR intervals. It reads:
- Apple Health
export.xml, read in slices, so a large export works; - FIT activity files from Garmin, Wahoo, COROS, Suunto and others, when they hold beat intervals;
- Polar Flow RR files and Polar Sensor Logger files;
- Movesense Showcase exports, and the RR files of Elite HRV, Welltory and Kubios;
- any plain list or table of RR intervals.
It does not open ZIP archives, so unzip first. For each recording it shows the date, length, number of beats and the share of likely artifacts Artifact An error in a heartbeat recording, such as a missed, extra or mistimed beat, often caused by movement or poor sensor contact. Artifacts can badly distort HRV numbers. More about Artifact , flagging an interval outside 300 to 2,000 ms or more than 25% away from the median of the beats around it, without changing any interval. You can download the beats as CSV, as Kubios text, or as a ZIP with a summary. If you drop an Oura, WHOOP or Fitbit file, it tells you the file holds HRV values, not beats.
The HRV Analyzer reads the same files, many at a time, from a folder or from inside a ZIP, up to 50,000 intervals per recording, about 12 hours. It marks beats that look like artifacts, corrects them, and works out RMSSD, SDNN and mean heart rate Mean RR The average time between heartbeats in a recording, in milliseconds. Heart rate is the same number upside down: 60,000 divided by the mean RR. More about Mean RR , or every metric in its Research mode. HRV artifacts and extra beats explains where artifacts come from and how correction works.
Both tools run in your browser. Files are read on your device and nothing is sent to us, not even the file name.
A file of readings or nightly values: a spreadsheet
Open the CSV in a spreadsheet and plot HRV by date. A few rules keep the chart honest:
- Compare like with like. One device, one statistic, one time of day. An Apple Watch SDNN reading, WHOOP’s Recovery HRV and Polar’s 4-hour average are different numbers, even on the same night. HRV by device lists what each maker reports.
- Don’t rebuild the app’s number. Averaging a night’s readings yourself gives a different figure from the app’s whenever the maker uses only part of the night or filters the readings first.
- Watch for breaks in the series. A new device, a different wear location or a software update can shift the numbers (can a software update change my HRV?). Mark the date and treat what follows as a new series.
- Read the trend, not the night. A 7-day average set against your own usual range tells you more than any single value; building your HRV baseline shows how.
An export is a record of numbers, not a diagnosis. If something in your data worries you, take it to a doctor with your symptoms.