How to measure heart rate on your smartwatch

Photo by Dan Seifert / The Verge

There are a lot of heart-rate monitoring features on modern watches. Spot checks as well as passive all-day monitoring are included. Some will alert you if your heart rate suddenly goes up. FDA-cleared electrocardiograms can help detect a condition called atrial fibrillation.

Just a decade ago, the smartwatches were basically pedometers. In practice, heart rate monitoring can be useful for people who want to understand more about their bodies or their fitness over time. Some athletes prefer to train in heart rate zones, which is hard to do unless you can check it in real time. Several people say that their watches saved their lives because of abnormal heart rate alert.

It's important to remember that these aren't medical devices. They aren't able to diagnose you with any sort of condition at the end of the day. Even if they were, doctors are still not sure how to handle the data that consumers collect on their own.

There are many reasons why you might get inaccurate readings. We will cover how to measure your heart rate and how to use a heart rate monitor. We will get into how to use the EKG feature with the current crop of smartwatches and what EKG- capable watches can and cannot do.

Vjeran Pavic / The Verge

How optical heart rate sensors work

When you flip the device over, the green LEDs are a photoplethysmography (PPG) sensor. The LEDs shine light into your skin and the light that's refracted back is translated into heart rate data. VO2 Max and heart rate variability are metrics that include your resting heart rate.

Over the years optical heart rate sensors have gotten better, but wrist-based PPG sensors still aren't always accurate. A recent study found that the sensors didn't work for people with darker skin. The wrist is not the best place for a sensor. There is a lot of noise from your arm movements, and a company has to be able to effectively filter that out. You could wear the same watch on each arm and still get different readings.

Fit is a factor. There are a few general tips for getting the most accurate data.

• Wear the watch about one finger length above your wrist bone
• Make sure there’s good contact between the sensor array and your skin
• Tighten the strap during exercise. You may also want to wear the device higher on the wrist.
• Wipe the sensor array clean whenever it gets dirty

Photo by Victoria Song / The Verge

Viewing heart rate and settings

You should use your watch's companion app to see the settings. You will be able to modify how often your watch measures your heart rate. Some watches measure heart rate continuously, while others measure periodically.

The Apple Watch can measure your heart rate when you are still and walking. When you are in a workout and three minutes after, it measures. You don't have the option to change it. You may be able to have more of a say with other devices. You can usually find heart rate settings in your device's settings or a health settings menu.

Your watch may be able to alert you of low and high heart rate. If your heart rate goes below or above a threshold, you will get a notification. If you sit still and your heart rate goes up to 120 beats per minute, you might get a notification. You can change the range on many watches.

We have outlined how to access settings for some of the most popular devices and how to measure your heart rate.

Apple Watch

Screenshot: Victoria Song / The Verge

To access heart rate settings, open the Watch app and scroll down the list of installed apps. You can enable a variety of health measures here.

• Toggling on Cardio Fitness Notifications will tell you when it deems your cardio fitness is low.
• Enabling Irregular Rhythm notifications means you’ll get notified if the watch identifies heart rhythms that may indicate atrial fibrillation.
• You can also set ranges for High Heart Rate and Low Heart Rate notifications. These notifications alert you when you’ve passed an abnormal threshold while you’re inactive.

None of these are diagnostic features.

To measure heart rate.

• Click the digital crown to bring up your apps
• Tap the Heart app (The app features a red background with a heart on it.)
• From there, you can manually start a heart rate reading
• You can also scroll down to view your resting heart rate and walking average heart rate

Fitbit trackers and smartwatches

You can access heart rate settings.

• Tap your profile icon in the upper left corner
• Scroll down to Settings
• Tap Activity & Wellness
• Tap Heart Settings
• From here, you can set customized high and low heart rate alerts, as well as heart rate zones for exercise

Another method is here.

• Tap your profile icon in the upper left corner
• Select the device’s profile
• Tap High & Low heart rate to customize these alerts.

To see the heart rate.

• From the clock face, swipe up to see current heart rate
• You can also view your rate in the Exercise app during exercise
• Certain clock faces will also feature heart rate as a complication
• You can also view in further detail from the Fitbit app dashboard

Samsung Galaxy Watches

The heart rate settings on the watch can be accessed.

• Head to the Samsung Health app on your watch
• Swipe down to Settings
• Tap Measurement and select the Heart Rate section
• From here, you can select whether you want to measure continuously, periodically (once every 10 minutes while still), or manually only

Photo by Chris Welch / The Verge

On the watches of Tizen.

• Press the power button on the watch
• Head to the Samsung Health app
• Swipe to Heart Rate and scroll to the bottom of the screen
• Tap HR and stress measurement
• After that, the options should be the same as above

To set up low heart rate alert:

• Head to the Samsung Health app
• Tap Heart rate
• Scroll down to HR and Stress Management or Auto HR settings
• Set your watch to measure heart rate continuously
• Tap More Options or the three dots
• Tap HR alert settings
• From here, you can customize your alerts

To measure heart rate manually.

• In the Samsung Health app, tap Heart rate
• Tap Measure

Photo by Amelia Holowaty Krales / The Verge

About EKGs

Only a few of the smartwatches have been approved by the FDA to measure electrocardiograms in the US. Even if the watch you buy supports this feature, you have to check to see if it has been granted regulatory clearance in your country.

The electrical signals from your heart are read by the EKGs on the smartwatches. You can create a closed circuit by touching your finger to the case or digital crown. After a short period of time, you will be told if your heart rhythm is normal or if you have signs of a problem.

No watch can give you an actual medical diagnosis. You can export the information to a PDF that you can share with your doctor. If you have a clean bill of health from your doctor, you don't need to use this feature at all.

You should be aware that you may get a few readings. There are several reasons why that can happen. If you are restless, that could result in an inconclusive result, so you have to remain very still to take the EKG readings. Your skin might be wet, and that can affect a reading.

The idea is to relax and keep still while using the EKG feature.

Apple Watch

Only the Apple Watch Series 4, 5, 6, and 7 can be used for EKGs.

Screenshot: Victoria Song / The Verge

How to start.

• Open the Health app on your phone and follow the prompts, or tap Browse > Heart > Electrocardiograms > Set Up ECG app
• You should then see the EKG app on your watch
• Tap the EKG app on your wrist
• Touch the Digital crown with a finger from your opposite hand
• Wait 30 seconds for the watch to take a reading

You can export your results.

• Open the Health app
• Tap Browse > Heart > Electrocardiograms
• From there, you should see a list of your readings
• Tap the one you want to generate a report for
• Tap Export a PDF for your doctor
• You can also tap the Share button to print or email the PDF, as well as upload it to services like Dropbox

Samsung Galaxy Watch

The only watches that support EKG readings are theGalaxy Watch Active 2 and theGalaxy Watch 3.

How to start.

• First, make sure your watch and phone are on the latest software
• Open the Samsung Health Monitor app on your watch
• Tap Download App. This should bring up the app download page on your phone.
• Tap Install
• Launch the Samsung Health Monitor app
• Tap continue and fill out information prompts
• Tap Finish. You should see a button that says Get Started.
• You’ll then have to follow some more onscreen prompts
• Select which wrist you’ll wear the watch on
• Hit Done
• You should now be able to take an EKG on your watch

You can export your results.

• Open the Samsung Health Monitor app on your phone
• Tap ECG and select View History
• Select the report you want to export
• Tap Share This Report
• Select the format you’d like to send (PDF, email, etc.)

Fitbit Sense and Charge 5

Only the Charge 5 and the Sense can take the readings.

Screenshot: Victoria Song / The Verge

If you don't already have the app on your watch or tracker, here's how to uninstall it.

• Tap your profile icon in the upper left corner
• Select device profile
• Tap Gallery
• You should see the High/Low heart rate app and the EKG app
• Tap the app icon to install / uninstall

How to start.

• Head to the Discover tab in the Fitbit app
• Scroll down to Assessments & Reports
• Select Heart Rhythm Assessment
• Read through the educational materials
• Open the ECG app on your watch or tracker.
• Place your finger and thumb on the edges of the case
• Wait 30 seconds and then view your results

You can export your results.

• Tap the Discover tab in the Fitbit app
• Scroll down to Assessments & Reports
• Select Heart Rhythm Assessment
• Tap View Results
• Select which one you want to generate a report for
• Tap Export a PDF for your doctor

Withings ScanWatch

The ScanWatch is the only watch cleared for use in the US.

How to start.

• Open the Health Mate app
• Select Devices, then ScanWatch
• Tap More Settings, and then ECG
• Select which wrist you’re wearing the watch on
• On your watch, use the side button to scroll to ECG Mode
• Press the side button
• Place your fingers on the top ring for 30 seconds

You can export your results.

• Your results should automatically appear in your Health Mate app feed
• Tap your results
• Scroll down to Share a Health Report and follow the prompts to create a PDF