Apple Watches do track sleep, but only if you wear them to bed and set up the Sleep app
Apple Watches have included sleep tracking since the Series 6 model in 2020. The watch measures how long you sleep and how much time you spend in REM, core, and deep sleep stages by monitoring your heart rate, movement, and breathing patterns throughout the night. However, the watch does not automatically detect sleep — you have to tell it when you plan to sleep by setting a bedtime in the Sleep app, or it will not record anything.
The data appears in the Health app on your iPhone the next morning. You see total sleep time, the breakdown of sleep stages, and a sleep score that compares your night to your recent average. The watch also tracks sleep interruptions and can wake you with a silent alarm if you set one.
Key Takeaways
- Apple Watch sleep tracking works on Series 6 and newer models, and requires you to set a bedtime in the Sleep app before you go to bed.
- The watch measures total sleep time and divides it into REM, core, and deep sleep stages using heart rate and movement data.
- Sleep data syncs to your iPhone's Health app each morning and shows a sleep score based on your recent pattern.
- Wearing the watch to bed and keeping it charged are the main requirements — the watch needs at least 30 percent battery to track sleep.
Which Apple Watch models include sleep tracking
Sleep tracking is available on the Apple Watch Series 6 and all newer models, including the Series 7, Series 8, Series 9, Ultra, and Ultra 2. If you own an older model — Series 5 or earlier — your watch cannot track sleep, even if you update the software.
The feature also works on the second-generation Apple Watch SE and later, but not on the original SE from 2020. Check your watch model in the Settings app under General, then About. If your model is not listed above, you will need a newer watch to use sleep tracking.
How to set up sleep tracking on your Apple Watch
Open the Sleep app on your watch and tap Add Bedtime. Choose your target bedtime and wake time, then set how many hours you want to sleep each night. The watch will send you a reminder 30 minutes before your bedtime so you can wind down.
On your iPhone, open the Health app, go to the Sleep tab, and turn on Track Sleep with Apple Watch. You can also set a sleep schedule here and adjust your bedtime and wake time. Once this is done, the watch will begin recording sleep data automatically each night when you wear it to bed.
The watch needs at least 30 percent battery to track sleep. If the battery drops below that level during the night, tracking stops. Charge your watch before bed if the battery is low, or use the charging dock in the morning and wear it during the day instead.
What the sleep stages mean and how they are measured
REM sleep is when most dreaming happens and your brain processes emotions and memories. Core sleep is lighter sleep that helps with physical recovery and memory formation. Deep sleep is the most restorative stage, when your body repairs muscle and bone and strengthens your immune system. A typical night includes all three, cycling through them multiple times.
The Apple Watch estimates these stages by monitoring your heart rate variability — the time between heartbeats — and your wrist movement. When your heart rate is steady and movement is minimal, the watch assumes you are in deep sleep. When your heart rate rises and movement increases, it assumes you are in REM sleep. The watch does not use brain waves like a sleep lab does, so the estimates are not as precise as a medical sleep study.
The sleep score shown in the Health app compares your night to your recent average. If you usually sleep seven hours and sleep six hours one night, your score will be lower. The score is meant to show trends over time, not to judge whether you slept "well" in an absolute sense.
How accurate is Apple Watch sleep tracking
Apple Watch sleep tracking is reasonably accurate for measuring total sleep time — studies show it typically comes within 30 minutes of actual sleep duration. However, the breakdown of sleep stages is less reliable. The watch often overestimates deep sleep and underestimates REM sleep compared to what a medical sleep study would show.
The watch is better at detecting when you are awake than at distinguishing between different sleep stages. If you lie still but awake in bed, the watch may record that as sleep. If you move around a lot during the night, it may record that as a lighter stage than you actually experienced.
For most people, the data is useful for spotting patterns — whether you are sleeping more or less than usual, or whether a change in routine affects your sleep. It is not precise enough to diagnose a sleep disorder, and you should see a doctor if you have concerns about your sleep quality.
Sleep tracking compared to other smartwatches and fitness trackers
Most smartwatches and fitness trackers now include sleep tracking. Garmin watches, Fitbit devices, Samsung Galaxy Watches, and Oura Rings all measure sleep stages using similar methods — heart rate and movement data. The accuracy is comparable across brands, with total sleep time usually within 30 minutes and stage breakdown less reliable than medical testing.
The main difference is how the data is presented. Fitbit shows a detailed breakdown and sleep insights. Garmin focuses on sleep quality and recovery. Oura Ring emphasizes readiness scores that combine sleep, heart rate, and activity. Apple Watch keeps the display straightforward with a sleep score and stage breakdown, and integrates the data into the Health app alongside other metrics like steps and workouts.
If sleep tracking is your main reason for choosing a smartwatch, the brand matters less than whether you will actually wear the device to bed consistently. A watch that sits on your nightstand will not track anything.
Tips for better sleep tracking data
Wear your watch snugly on your wrist — loose watches move around and give inaccurate readings. The watch needs skin contact to measure your heart rate, so avoid wearing it over a long sleeve or under a wristband.
Charge your watch before bed so it has enough battery to last the night. If you charge it in the morning instead, you will miss that night's data. Some people charge their watch for 30 minutes before bed and then wear it through the night.
Keep a consistent sleep schedule. The sleep score compares your night to your recent average, so irregular bedtimes and wake times make the data less meaningful. If you sleep at very different times on weekends versus weekdays, the watch will show that variation in your score.
Do not expect the watch to catch every detail. If you care about precise sleep stage data for medical reasons, a sleep study in a lab is more accurate. The watch is best used to track whether your sleep is improving or getting worse over weeks and months.
Frequently Asked Questions
Do I have to wear my Apple Watch to bed every night for sleep tracking to work?
Yes. The watch only records sleep on nights when you wear it to bed. If you skip a night, that night will not appear in your sleep history. You can still see your average sleep time over the past week or month, but individual nights without the watch will be missing.
Can I use sleep tracking without setting a bedtime in the Sleep app?
No. The watch needs you to set a bedtime first. If you just wear the watch to bed without setting a bedtime, it will not record sleep data. You can set the bedtime a few minutes before you go to sleep if you prefer not to plan ahead.
What does the sleep score number mean?
The sleep score compares your sleep to your recent average. If you usually sleep seven hours and you sleep seven hours one night, you might get a score of 100. If you sleep only six hours, your score might be 85. The number is relative to your own pattern, not a universal standard of good sleep.
Will my Apple Watch track sleep if the battery dies during the night?
No. The watch stops tracking if the battery drops below 30 percent. If your battery is low when you go to bed, charge the watch for at least 30 minutes before sleep, or you will lose that night's data.
Is Apple Watch sleep tracking accurate enough to diagnose a sleep problem?
No. The watch is accurate for total sleep time but less reliable for sleep stages. If you think you have a sleep disorder, see a doctor who can order a proper sleep study. The watch is useful for tracking your own patterns over time, not for medical diagnosis.