Written by Robyn

How does the heart rate monitor on the Apple Watch work?

I like to closely monitor my heart rate and the Apple Watch helps me with that. The Apple Watch Series 5 is very accurate, thanks to the electrical heart rate sensor (ECG) and the improved optical heart rate monitor. The series 3 only has an optical heart rate sensor. We'll tell you the difference between ECG and the optical heart rate sensor and how you can measure your heart rate with the Apple Watch.

Get started with the heart rate monitor on your Apple Watch

You can easily measure your heart rate with the Apple Watch. There are various types of heart rate measurement available.

  • With the Apple Watch Series 5, you can measure your heart rate using the electrical heart rate sensor.
  • With the Apple Watch Series 3, you can measure your heart rate using the optical heart rate sensor.
  • View your heart rate measurements on your Apple Watch.
  • Turn on heart rate notifications on your Apple Watch.

Heart rate measurement on the Apple Watch Series 5: ECG

Apple Watch Series 5 ECG electrical heart rate sensor

In addition to an optical heart rate sensor, the Apple Watch Series 5 has a new ECG function. The electrical heart rate sensor determines the timing and intensity of your heart rate by measuring your heart's electrical signals. You can measure your heart rate more accurately with the ECG and easily make cardiograms from your wrist. Open the ECG app on the Apple Watch Series 5 and place your finger on the Digital Crown. The Apple Watch Series will make a cardiogram with the ECG function.

Heart rate measurement on the Apple Watch Series 3: optical

Apple Watch Series 3 optical heart rate sensor

The Apple Watch Series 3 doesn't have an electrical heart rate sensor like the Apple Watch Series 5, but an optical heart rate sensor. It uses green LED lighting. These lights blink hundreds of times per second, so my Apple Watch can measure the amount of blood flowing through my veins during that time. When my heart is beating, the lights detect more blood than when my heart isn't beating.

Measure and view your heart rate

Measuring heart rate with Apple Watch

To measure your heart rate as accurately as possible, it's important that your Apple Watch fits properly around your wrist and the heart rate sensor touches your skin. As long as you're wearing the Apple Watch on your wrist, it will measure your heart rate. You'll gain valuable insight into your heart rate during exercise as well, because the heart rate measurement is integrated into the Workout app. To view your current heart rate, resting heart rate, and average heart rate, open the Heart Rate app on your Apple Watch.

How do you set up heart rate notifications on your Apple Watch?

Via heart rate notifications, your Apple Watch warns you if your heart rate is irregular when you're not active. That way, I'll be notified when my heart rate is too high or too low, for example when I'm watching my favorite series.

  1. I open the Apple Watch App on my iPhone.
  2. I navigate to the My Watch tab and tap Heart.
  3. This is the overview with all the options for the heart rate monitor.
  4. Tap High Heart Rate. I can choose how many beats per minute my Apple Watch should at least detect before sending me a notification.
  5. Choose 'Low Heart Rate'. I can choose the minimum amount of beats per minute. Anything below this number means I'll get a warning.


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