Google's heart rate articles say the Pixel Watch uses an optical sensor with flashing green LEDs that detect blood volume changes in the wrist, and tracking is on by default. Wear the watch on top of the wrist with the back in contact with the skin, about a finger's width above the wrist bone at rest, a bit tighter and higher during exercise, snug but not constricting because a tight band restricts blood flow. Air temperature, stress, alcohol or caffeine, illness and medication change heart rate, and cold weather can hinder readings during exercise.
A blank or gray reading means the watch is searching for a stronger signal: relax your wrist and hold still for up to 10 seconds. Use the Exercise app so heart rate and GPS record together. The Google ECG app, installed from Google Play in select countries, checks heart rhythm for signs of AFib but only a doctor can diagnose it; it is not for people under 22, and metal mesh or slim bands are incompatible with ECG on the original Pixel Watch. Keep the watch away from pacemakers and implanted devices.
Differential
Likely causes of “Google Pixel Watch heart-rate readings are missing or inaccurate”, and how to tell them apart
- 1
A loose band or the watch too low
What separates it The readings drop during exercise because of a loose band or the watch being too low
How to confirm Wear it higher and a bit tighter for exercise
- 2
Vigorous arm movement
What separates it There is a blank reading in HIIT or boxing because of vigorous arm movement
How to confirm Relax the wrist and hold still for up to 10 seconds
- 3
Cold weather
What separates it There is no reading outdoors because of cold weather
How to confirm Warm the wrist, and take the reading again
- 4
A metal band
What separates it ECG fails on the original Pixel Watch because of a metal band
How to confirm Use an approved band, and take the reading again
- 5
Heart rate tracking is off
What separates it There are no readings because heart rate tracking is off
How to confirm Turn tracking on in Google Health, and take the reading again
Before you touch a setting
Record this first — changing settings destroys the evidence
- Which reading fails and during what activity
- How the watch is worn and the band type
- Whether you are in a country where the ECG app is available
Try in this order
0 of 7 completedCheck tracking is on
ReversibleCheck tracking is on, by opening the heart rate settings in Google Health, and then test again to see whether it helped.
Fix the fit
ReversibleFix the fit, by wearing the watch on top of the wrist with the back touching your skin.
Adjust for exercise
ReversibleAdjust for exercise, by wearing the watch a bit tighter and higher up the wrist.
Hold still
ReversibleHold still, and if the reading is gray, relax and stay still for up to 10 seconds.
Use the Exercise app
ReversibleUse the Exercise app, and record workouts with the watch so that the readings are logged.
Change the band
ReversibleChange the band, and use a compatible band for ECG readings on the watch, and then test again to see whether it helped.
Restart
ReversibleRestart the watch, and re check the reading once it comes back on, and then test again to see whether it helped.
Model-specific
What is true of this model and not of its siblings
- Sensors by model
- Google's specifications list a multi-path optical heart rate sensor, red and infrared sensors for SpO2 and multipurpose electrical sensors compatible with the ECG app on the newer Pixel Watch models.
- ECG availability
- Google says the ECG app is only available in select countries and not intended for people under 22.
- Repair cost
- Fit and settings cost nothing. A dead sensor is a hardware fault; Google does not repair a Pixel Watch 3, and Preferred Care is $4 a month or $89 for two years plus a $49 service fee, per 9to5Google.
- Other models this page answers
- These steps also fit the Pixel Watch 2.
Stop boundary
When this stops being a self-service repair
- !If readings are absurd on both wrists, contact Google support
- !If you have symptoms such as chest pain or dizziness, contact a doctor rather than relying on the tracker
- !If the ECG app is unavailable, it is limited to select countries
Evidence ledger
Sources behind this answer
Sensor, fit, position and factors.
Blank or gray readings and the tips list.
Heart rate tracking, the ECG app and medical device interference.
Band materials and ECG compatibility.
The Pixel Watch line and its generations.
Exact questions
Common questions
How does the sensor work?+
Flashing green LEDs detect blood volume changes in wrist capillaries.
Is ECG on every model?+
The Google ECG app is on Pixel Watch models with the electrical sensor and only in select countries.
Can the ECG diagnose AFib?+
No, only a doctor can; it shows signs.
Does the band matter?+
Metal Mesh and Metal Slim bands are incompatible with ECG on the original Pixel Watch.
Do sweat and lotion matter?+
Google lists air temperature, stress, caffeine, alcohol, illness and medication among the things that change heart rate, and a watch that is too tight restricts blood flow, so comfort and fit matter as much as the sensor.
Can it interfere with a pacemaker?+
Keep the watch and charger away from implanted devices and ask your doctor.
What affects heart rate?+
Stress, caffeine, alcohol, illness, medication and temperature.