You glance at your Galaxy Watch8 during a brisk walk and the heart rate number looks impossible, frozen, or wildly out of step with how hard you are actually working. Maybe it reads low while you are climbing stairs, jumps around at rest, or simply refuses to settle on a believable figure. The good news is that the 44mm Galaxy Watch8 has a capable optical heart rate sensor and an electrical (ECG) sensor built into its BioActive Sensor, so the hardware is almost certainly fine. The readings usually go wrong because of fit, a dirty sensor, the wrong measurement conditions, or a software hiccup. Work through the steps below in order, starting with the quickest and safest, and save the reset and service options for last.
Get the fit and position right first
A loose or poorly positioned watch is the single most common reason heart rate readings come out wrong. The optical sensor on the back needs steady, even contact with your skin, and any gap lets in stray light that confuses the reading. This is the first thing to fix because it costs nothing and solves most accuracy complaints on its own.
Wear the Galaxy Watch8 snugly above the wrist, but do not fasten the band too tightly. If you have thin wrists, adjust the position of the heart rate sensor to the right, left, up, or down on your wrist, or turn the watch so the heart rate sensor sits firmly against the inside of your wrist. A small adjustment here often clears the problem immediately.
Clean the back sensor and clear anything between it and your skin
The sensor reads your pulse by shining light into your skin and measuring what reflects back, so anything in the way distorts the result. If the heart rate sensor on the back of the watch is dirty, wipe it and try again. Also remove any protective plastic that may still be covering the sensor before you measure.
Body hair, dirt, or other objects sitting between the band and your wrist can stop the sensor light from reflecting evenly and produce inaccurate readings. A quick wipe of both the sensor and the skin underneath it can be the difference between a steady reading and a jumpy one.
Measure under the conditions the sensor expects
The optical sensor is sensitive to movement and to your physical state at the moment of the reading. For the most accurate result, take the measurement while seated and relaxed. Do not move your body while taking heart rate measurements, and do not talk, yawn, or breathe deeply during the reading.
Cold temperatures can affect the optical sensor, so keep your wrist warm when measuring in cold weather. If a single result looks abnormal, wait a moment and measure again rather than trusting one odd number.
- 1.Open Samsung Health on the watch.
- 2.Swipe to and tap "Heart rate."
- 3.Tap "Measure" and hold still until the reading completes.
Confirm the measurement mode in Samsung Health
If the watch is not recording heart rate the way you expect, for example showing only occasional readings when you wanted continuous tracking, check the measurement frequency setting. The watch can read on demand only, on a schedule, or continuously, and the wrong mode can look like missing data rather than inaccurate data.
On the watch, go to Samsung Health > Settings > Heart rate, then choose one of the available options: "Measures continuously," "Every 10 mins while still," or "Manual measurement only." Choosing continuous, or every 10 minutes while still, keeps the watch tracking throughout the day instead of only reading when you ask it to.
Restart the watch to clear temporary glitches
A reboot clears the kind of temporary sensor and software glitches that can freeze or skew heart rate readings. Try the gentle restart first before forcing one.
To restart from the watch interface, swipe down to the quick panel, tap Power, then tap Power off and turn the watch back on. You can also hold the Home (Power) button to restart. If the watch is unresponsive, force a restart by pressing and holding the Home button (also labeled Power) and the Back button at the same time for at least seven seconds, until the screen goes black and the Samsung logo appears. On some models it can take up to about 30 seconds for "Rebooting..." to appear, so do not let go too early.
Update the watch software and the companion app
Outdated firmware can cause sensor and tracking problems, so check for updates on both the watch and the Galaxy Wearable app if issues persist after rebooting. Make sure the watch has at least a 30% charge before you start, since an update will not run on a low battery.
On your connected phone, open the Galaxy Wearable app > Watch settings > Watch software update > Download and install. You can also update directly on the watch by going to Settings > General > Watch software update and confirming the download. Installing the latest software keeps the sensor firmware current and resolves bugs that earlier versions may have introduced.
Unpair and re-pair the watch with your Android phone
If readings still will not sync correctly between the watch and your phone, removing and re-adding the watch rebuilds the connection cleanly. This step applies to Android only: the Galaxy Watch8 pairs only with Android 11 or higher phones that have Google Mobile Services, and it does not support iPhone or iOS, so there is no iPhone re-pair path for this model.
Open the Galaxy Wearable app on your Android phone, remove the current watch from the app, then run the setup again to re-add it. The Galaxy Wearable app is the official tool Samsung uses to pair, update, and manage the watch, so handling both the unpair and the re-pair through it keeps the connection consistent.
Back up, then factory reset as a last software step
If nothing above has fixed the readings, a reset returns the watch to its default settings and clears deeper software issues. This step erases everything, so back up first using the Galaxy Wearable app or your Samsung account on the watch before you proceed. The official warning is clear, that all of your personal data will be removed and the watch will restore back to its default settings.
To reset on the watch, go to Settings > General > Reset, then tap the checkmark to confirm. You can also reset from the phone by opening the Galaxy Wearable app > Watch settings > General > Reset > Reset to confirm. After the reset, set up the watch again and re-test your heart rate readings under good conditions.
When to request service from Samsung
If your heart rate readings are still inaccurate after working through fit, sensor cleaning, measurement conditions, settings, restart, updates, re-pairing, and reset, the sensor itself may need attention. At that point it is worth having the hardware checked rather than chasing the problem in software.
Contact Samsung Support to have the watch inspected or to request a repair. As a useful safeguard in the meantime, you can set a high or low resting heart rate alert in Samsung Health, available on Wear OS Galaxy Watch models, so the watch warns you if a reading looks abnormal.
Frequently Asked Questions
Why is my Galaxy Watch8 heart rate reading too low or jumping around?
The most common causes are a loose or badly positioned watch, a dirty sensor, or measuring while moving. Wear the watch snugly above the wrist (without overtightening), wipe the back sensor, and take the reading while seated and relaxed without moving, talking, or breathing deeply.
How do I measure my heart rate manually on the Galaxy Watch8?
Open Samsung Health on the watch, swipe to and tap "Heart rate," then tap "Measure." Stay still and quiet until the reading completes for the most accurate result.
Does cold weather affect Galaxy Watch8 heart rate accuracy?
Yes. Cold temperatures can affect the optical sensor, so keep your wrist warm when measuring in cold weather. Warming up before you take a reading helps the sensor get a clean signal.
Will resetting my Galaxy Watch8 delete my data?
Yes. A reset removes all of your personal data and restores the watch to its default settings, so back up first using the Galaxy Wearable app or your Samsung account on the watch. Only use the reset after the other fixes have not worked.
Can I use the Galaxy Watch8 with an iPhone to fix sync issues?
No. The Galaxy Watch8 does not support iPhone or iOS. It relies on Google Play services and pairs only with Android 11 or higher phones that have Google Mobile Services, so the unpair and re-pair steps apply to Android phones only.