Apple Watch sleep tracker: how it works and how to set it up

Using the Apple Watch as a sleep tracker

The Apple Watch sleep tracker is the default choice for iPhone owners, because sleep tracking is built into the watch and the Health app and does not need a subscription. It records when you slept, estimates your sleep stages and, with recent software, gives you a sleep score. This guide explains how the feature works, how to set it up in a few minutes and where its limits are. Product names are trademarks of their owners. We are not affiliated with any brand mentioned, and features, models and prices change, so check the maker's page before you buy.

Availability of specific features depends on the watch model, the version of watchOS and your region, so confirm the details on Apple's website for your device.

What the Apple Watch measures during sleep

The watch uses its motion sensor and optical heart-rate sensor to work out when you fall asleep and wake up. It then classifies the night into awake, REM, core and deep sleep. Core sleep is Apple's name for light sleep, stages 1 and 2. Recent watches also record overnight heart rate, respiratory rate and wrist temperature, and the Vitals feature in the Health app shows how these compare with your normal range.

Sleep stages and sleep score

Sleep stages were added in watchOS 9. A sleep score, out of 100, arrived with watchOS 26 on supported models. Reports describe it as built from sleep duration, bedtime consistency and interruptions, and Apple has adjusted how score ranges are labelled in later updates. As with other brands, the score is a convenient summary and not a medical measure. Look at how it moves over weeks, and ignore small swings from night to night.

Sleep apnea notifications

On supported models, the watch can look for patterns of breathing disturbance during sleep and, after a period of data, notify you that you may have sleep apnea. It is a screening feature cleared for use in some regions, not a diagnostic test. If you receive a notification, or if you snore loudly, stop breathing at night or feel very sleepy in the day, speak to a doctor. A sleep study is the way to confirm it.

How to set up sleep tracking

Open the Health app on your iPhone, choose Browse, then Sleep, and set up a sleep schedule with a bedtime, wake-up time and sleep goal. Turn on Sleep Tracking with Apple Watch. On the watch, Sleep Focus quiets notifications at bedtime. Wear the watch snugly but comfortably on the wrist you normally use. Make sure the watch has enough charge to last the night, and choose a time in the day to top it up, for example while you shower or get ready in the morning.

Battery life and charging habits

The biggest barrier to Apple Watch sleep tracking is battery. A watch that is dead at 10 PM tracks nothing. Many wearers charge it for 20 to 30 minutes before bed or in the morning, which is enough to cover the night, since sleep tracking uses little power. Low power mode and turning off always-on display at night can help. Third-party apps may need more battery than the built-in feature.

How accurate is it?

Reviews and studies suggest that Apple Watch sleep and wake detection is comparable to other leading wearables, with the usual caveat that sleep stages are estimates. It can overestimate sleep if you lie still, and it can miss short naps. The best way to judge it is to compare it with your own impression and with a sleep diary for two weeks.

Third-party sleep apps for Apple Watch

Apps such as AutoSleep, Pillow and Sleep Cycle offer extra features, including a smart alarm, sleep analysis and sleep sounds. Some are free with in-app purchases and some are one-off purchases. Check the permissions, and prefer apps that store their data in Apple Health so that it stays in one place. See our guides to sleep tracker apps, the sleep cycle app and free sleep tracker apps.

Turn the data into better sleep

The watch tells you what happened; you decide what to change. Use the bedtime calculator to pick a bedtime that matches whole sleep cycles, the caffeine cutoff calculator to protect your night and the wind-down timer to build a routine. Review your weekly average in the Health app on Sunday, and avoid obsessing over a single poor night.

Apple Watch sleep tracking versus rings and bands

The Apple Watch does a lot more than sleep: calls, payments, workouts, maps and safety features. The trade-off is that you must charge it daily and wear a larger device in bed. A smart ring is smaller and lasts days between charges, but focuses on sleep, readiness and activity and may need a membership. A Whoop-style band has no screen and a subscription at its core. If you already own an Apple Watch, your first step is to try its built-in sleep tracking for two weeks before buying anything else.

Troubleshooting Apple Watch sleep tracking

If sleep is not recorded, check that Sleep Tracking is on in the Health app, that the watch has enough charge, that you are wearing it snugly, that your sleep schedule is set and that the watch has its latest software. If the times look wrong, edit the schedule and make sure the Sleep Focus is active. Occasionally the watch counts quiet time in bed as sleep or misses a short nap. In such cases rely on your own sense and a diary.

Privacy and your Apple Health data

Apple Health stores data on your device and can sync it to iCloud with encryption. Third-party apps can read it only if you grant permission, and you can review and revoke access in the Health app at any time. Be selective about which apps you allow to read sleep data. You can also export your Health data from your profile.

Frequently asked questions