Check your heart rate on Apple Watch
Your heart rate is an important way to monitor how your body is doing. You can check your heart rate during a workout; see your resting, walking, breathe, workout, and recovery rates throughout the day; or take a new reading at any time.
See your heart rate
Open the Heart Rate app 
on your Apple Watch to view your current heart rate, resting rate, and walking average rate.
Your Apple Watch continues measuring your heart rate as long as you’re wearing it.
Note: Heart rate features are found on Apple Watch Series 1 and later.
Check your heart rate during a workout
By default, your current heart rate shows on the Multiple Metric workout view. To customize which metrics appear during a workout, follow these steps:
Open the Apple Watch app on your iPhone.
Tap My Watch, go to Workout > Workout View, then tap a workout.
For more information, see Start a workout on Apple Watch.
See a graph of your heart rate data
Open the Health app on your iPhone.
Tap Health Data, then tap Heart.
You can see your heart rate over the last hour, day, week, month, or year. You can also see your resting, recovery, workout, walking average, and breathe rates; the maximum and minimum heart rates during the selected time period; and your heart rate variability.
Turn on heart rate data
By default, your Apple Watch monitors your heart rate for the Heart Rate app, workouts, and Breathe sessions. If you’ve turned off heart rate data, you can turn it back on.
Open the Apple Watch app on your iPhone.
Tap My Watch, then tap Privacy.
Turn on Heart Rate.
Receive heart rate notifications
Your Apple Watch can notify you if your heart rate remains above a chosen threshold or below a chosen threshold after you’ve been inactive for at least 10 minutes. You can turn on heart rate notifications when you first open the Heart Rate app, or at any time later.
Open the Apple Watch app on your iPhone.
Tap My Watch, then tap Heart.
Tap High Heart Rate, then choose a heart rate—120 bpm, for example.
Tap Low Heart Rate, then choose a heart rate—45 bpm, for example.
About Irregular Rhythm Notifications (not available in all regions)
You can now receive a notification if Apple Watch has identified an irregular heart rhythm that appears to be atrial fibrillation (AFib). This feature is available on Apple Watch Series 1 or later with watchOS 5.1.2 or later. For more information about Irregular Rhythm Notifications, see the Apple Support article Heart rate notifications on your Apple Watch, and the document Instructions for Use: Irregular Rhythm Notification Feature.
About the ECG app (not available in all regions, Apple Watch Series 4 only)
Apple Watch Series 4 has an electrical heart rate sensor which, along with the ECG app 
, allows you to take an electrocardiogram (or ECG). The ECG app is only available with watchOS 5.1.2 or later. For more information about the ECG app, see the Apple Support article Taking an ECG with the ECG app on Apple Watch Series 4, and the document Instructions for Use: ECG App.
Note: For best results, the back of your Apple Watch needs skin contact for features like wrist detection, haptic notifications, and the heart rate sensor. Wearing your Apple Watch with the right fit—not too tight, not too loose, and with room for your skin to breathe—keeps you comfortable and lets the sensors do their job. You may want to tighten your Apple Watch for workouts, then loosen the band when you’re done. Water may prevent, or reduce the accuracy of, heart rate monitoring. In addition, the sensors work only when you wear your Apple Watch on the top of your wrist. For more information, see the Apple Support article Your heart rate. What it means, and where on Apple Watch you’ll find it.