Ranked by how much battery each change actually returns, rather than by how often the tip gets repeated. Do the first two and most people stop having the problem.
1. Turn off the always-on display
The largest single cost by a wide margin, because it is the difference between the screen being dimly lit all day and lit only when you look at it. Settings, Display & Brightness, Always On.
Worth being honest that this is a real downgrade in how the watch feels to use. It is also the only change on this list that reliably converts a watch that dies by evening into one that does not.
2. Rule out a recent update
After a watchOS update the watch reindexes, re-syncs and rebuilds caches, and battery life is genuinely worse for a couple of days. This is the single most common cause of “it was fine last week”.
Give it two or three full charge cycles before changing anything else. If it is still bad after a week, move on down the list.
3. Check Battery Health before blaming settings
Settings, Battery, Battery Health. Maximum capacity below about 80 percent means the cell has degraded and no setting will bring the runtime back.
Doing this early saves an evening of turning off features that were never the problem. It is also the check that tells you whether you are troubleshooting or shopping.
4. Fix the connection to your phone
When the watch loses Bluetooth to the iPhone it falls back to Wi-Fi or cellular, both of which cost considerably more power. A watch that spends the day disconnected drains noticeably faster.
If your watch frequently shows the disconnected indicator, that is the problem to solve rather than a symptom to work around. Unpair and re-pair is the heavy-handed fix and it does work.
5. Prune background app refresh and notifications
Settings, General, Background App Refresh. Turn it off for anything you do not actively use on the wrist. Same for notifications: every one wakes the screen and buzzes the motor, and the cumulative cost of a busy group chat is not small.
6. Workouts and GPS, in proportion
Outdoor workouts with GPS are genuinely expensive, and a long run or ride will visibly move the battery. This is the watch doing its job rather than a fault. If you do long sessions and want to sleep in it too, that is an argument for an Ultra rather than for a settings change.
What not to bother with
Closing apps. watchOS suspends them anyway. This does nothing and is repeated endlessly.
Turning off the heart rate sensor. It saves very little and it disables sleep tracking, HRV, and every health feature that makes the watch worth wearing. A false economy.
Low Power Mode all day. It works, and it turns off background heart rate and blood oxygen, which means you stop collecting the data. Fine for a specific long day, bad as a permanent setting.
If the watch is not recording nights at all, that is a different problem: Apple Watch not tracking sleep.