Is it normal for Apple Watch battery to drop 10% in an hour?

It depends entirely on what that hour contained. An hour of a GPS outdoor workout with music over Bluetooth can cost far more than an hour of sitting at a desk, where the watch may use only a percent or two. Because the battery is small, each percentage point is a small amount of energy, so the same activity moves the number much more than it would on a phone. Compare like with like: same watch face, same activity, same signal, before you call it a fault.

Does turning off Bluetooth or Wi-Fi on Apple Watch save battery?

Not meaningfully, and it can cost you. The watch keeps a low-power link to the phone for notifications, and losing it pushes work onto Wi-Fi or cellular, which is more expensive. The real savings are the screen, the workout modes, and cellular use away from the phone. Turn off the always-on display or choose a dimmer, simpler watch face before you start switching radios off.

Why does the battery percentage on my watch and my phone disagree?

Because they are two separate measurements. The watch reports the state of its own battery from its own gauge, and the phone's battery complication is a reported value that refreshes on its own schedule, not continuously. A small, temporary gap is the normal cost of two devices reporting independently. A large gap that persists after both have been on the charger is worth a closer look.

Why Apple Watch Battery Drains Faster Than iPhone

Short answer: because it is a different kind of battery doing a different kind of job. An Apple Watch battery holds a small fraction of what an iPhone battery holds, and it feeds a screen that never fully sleeps plus a heart-rate sensor that samples all day. The phone spends most of its life with the screen off; the watch almost never does. Both devices are working as designed — they are just counted on different scales.

Why one is measured in days and the other in hours

Two things separate them, and only the first one is about size.

1. The battery is far smaller — so every percent is smaller. Apple does not publish Apple Watch battery capacity in mAh, the same way it does not publish iPhone capacity; it publishes usage estimates instead. But you do not need a figure to see the point. A phone battery has to carry a 6-inch-class display and a cellular radio through a day. A watch battery has to carry a display and sensors on a case that weighs less than a phone's camera bump. A one-percent drop on a watch is a much smaller amount of energy than a one-percent drop on a phone — which is exactly why the number feels like it moves faster.

Think of it as two fuel tanks of very different size on the same road. The small tank empties sooner at the same fuel economy. That is not a defect in the tank.

2. The screen is on almost continuously — and the sensors never stop. On a phone, the display is the biggest consumer but it is off most of the day. On a watch, the display is woken constantly by wrist raises and, if you use it, kept dimly lit by the always-on display, and the heart-rate sensor runs continuously in the background. Those are fixed costs a phone simply does not pay.

That is why Apple's own battery specification for a watch is expressed as a description of a day — a certain number of time checks, a certain number of notifications, a workout of a certain length — while an iPhone is specified in hours of particular use. Neither number is "how long it lasts". Both are "how long it lasts if you do this".

What actually moves Apple Watch battery, in order

This is the ordering that matters, because the settings people usually reach for first are the ones that matter least.

1. The screen. It is the largest single item, and the biggest lever you have. The always-on display is the headline cost: it keeps the display lit at a reduced refresh rate all day rather than only when you raise your wrist. Settings → Display & Brightness → Always On turns it off, and it is the one change that produces enough of a difference to notice. The watch face matters too, more than people expect — a bright, busy face with several complications redraws far more than a simple dark one, and complications that fetch data are doing work behind the scenes. Auto-launch of the last-used app on wrist raise (Settings → General → Return to Clock) is in this group as well.

2. Workouts, especially outdoors. A workout is the most expensive thing a watch does, and the modes differ by an order of magnitude. Outdoor workouts with GPS tracking and real-time heart rate are the heaviest; indoor workouts that rely on the phone for location, or do not need location at all, are far lighter. Playing audio from the watch itself over Bluetooth while training adds another radio to the same hour. If you want to compare two days fairly, hold the workout constant first — a day with a 60-minute outdoor run is not the same battery day as one without, and it never will be.

3. Cellular away from the phone. If your watch has cellular and you leave the phone behind, everything — notifications, messages, calls, streaming — runs over the cellular radio, which costs more than the short-range link to the phone. Nothing needs to be done about this; it is simply the biggest single variable in a day, and it explains a lot of "it died early today" reports.

4. Background activity from third-party apps. This is genuinely fourth, not first. Apps that run on the watch, refresh in the background, or use location add up, but they sit behind the screen, the workout and the radio.

Everything else — Bluetooth, Wi-Fi left on, notifications arriving — is rounding error.

What to change, and what to leave alone

In this order:

Turn off the always-on display if you can live without it. This is the single largest saving available, and it is reversible.
Use a darker, simpler face with fewer live complications.
Trim the heaviest complications only — those that fetch data on a schedule. Removing all of them is unnecessary.
Prefer workout modes that match what you are doing. Indoor modes where you do not need GPS; leave the phone within range when you do not need cellular.
Check the actual evidence before changing anything else. On the watch: Settings → Battery shows what consumed power. On the phone: the Watch app → General → Battery, and the phone's own Settings → Battery shows the watch as a separate row when it is connected.

Leave these alone:

Bluetooth and Wi-Fi. Leaving them on costs almost nothing, and switching them off can push work onto a more expensive radio. See iPhone Battery Saving: The Settings That Actually Matter — the same logic applies here, with the screen mattering even more.
A dark or plain face is not "boring", it is cheaper. That is the whole mechanism, not a placebo.
Charging the watch to 100% every night is fine, but if you care about its long-term fade, use Optimized Battery Charging (Settings → Battery → Battery Health) so it is not held at full for hours. See Charge Limit: Is 80% Worth It?.

The percentage is not the same unit as on your phone

This is the part that produces most of the anxiety, and it is worth stating plainly: a percentage is a percentage of a much smaller tank.

If your phone goes from 100% to 85% over a morning, that is a comfortable fraction of a day's capacity and you think nothing of it. If your watch goes from 100% to 70% over the same morning, that sounds alarming — but it is the same story told on a smaller tank. The watch will still reach the evening, because that is what it was designed to do; it simply spends its budget faster relative to its size.

The practical consequence: do not compare the two numbers to each other. Compare your watch to your watch. Same face, same routine, same signal, today versus last week. That comparison is meaningful. Watch-versus-phone is not.

After a watchOS update, the numbers will look wrong for a few days

The most common "my watch suddenly drains fast" reports cluster in the days after an update, and there is a real mechanism behind them:

The watch re-indexes and re-does background work after a system update — search data, media, and background tasks are rebuilt, and that work happens while you are also using the watch normally.
Optimized Battery Charging re-learns your routine. After an update the model of when you normally charge is being rebuilt, so the watch may charge differently for a few days.
A newly compiled or newly installed watch face and its complications can be doing setup work in the first days.
Watch and phone can be re-syncing data across the link, which is radio time.

None of that is a fault, and none of it is permanent. Give it two to four days of normal use before drawing conclusions. If the drain is still clearly worse after that, and Settings → Battery shows a specific app or workout mode at the top of the list, then you have something to act on — and it will be an app, not "the update". For the phone-side version of this pattern, see iPhone Battery Health Explained.

"The watch says 62%, the phone says 55%" — this is normal

The two readings come from two independent batteries with two independent gauges, and the phone's copy of the watch's number is a reported value, refreshed on a schedule, not a live feed. Add the delay of the Bluetooth link and it is entirely normal for the phone to show a slightly stale or slightly different figure.

A few details worth knowing:

The watch's own reading is the authoritative one. Its battery, its gauge. When you need to know whether you can leave the charger, look at the watch.
Small gaps of a few percent are display lag, not loss. They usually close as soon as both devices have been near each other, or after both are charged.
The number that means something is a large gap that survives both devices being charged and reconnected. That is a sync or pairing question, not a battery-capacity question.
Rounded reporting is normal. Some places on the phone show the watch's battery in coarse steps, which makes an unstable-looking gap out of nothing.

A watch and a phone disagreeing about battery percentage is the expected behaviour of two devices measuring themselves separately. It is evidence that both are reporting honestly, not evidence that something is broken. If you want to check the watch's own battery health over time, use the watch's Settings → Battery → Battery Health — see Battery Health by iPhone Model for how the 80% Service threshold works on the phone side, which is the same consumable logic.

Three myths worth dropping

"The watch drains faster, so its battery is faulty." Different tank, different job, different unit. Most "fast drain" is the always-on display plus a heavy face, and it is measurable in Settings → Battery.
"Turning off Bluetooth saves watch battery." It usually does the opposite — the low-power link to the phone is cheaper than doing the same work over Wi-Fi or cellular.
"The watch and phone should show the same percentage." They cannot. Two gauges, two batteries, one of them reporting to the other on a schedule. See iPhone 17 Battery and Heat for how Apple publishes usage estimates rather than capacity — the watch is the same policy in a smaller case. And if you want the ceiling: Apple does not publish watch battery capacity, so any mAh figure you see quoted is a teardown, not a specification.