Why is my iPhone battery draining so fast? Causes and fixes that actually help

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Your iPhone was lasting all day and now it struggles to reach the evening. Before assuming the battery is worn out, it is worth finding out what is actually using the power. Very often it is one app, one setting or a recent update, and that can be fixed for free.

First, look at the battery screen

Go to Settings, then Battery. The graph shows your battery level over the last 24 hours and 10 days, and the list underneath shows which apps used the most power. Tap an app to see how much of that was on screen and how much in the background.

If one app has a large share and you barely used it, it is the first suspect.
A lot of background activity from an app you do not need running is easy to fix (see below).
The suggestions at the top of the screen are specific to your phone and worth reading.

Just updated? Give it a day or two

After a major iOS update, the phone re-indexes photos, messages and files in the background, and battery life often looks worse for a few days. If it does not settle after that, carry on with the steps below.

The usual culprits

Screen brightness: the screen is usually the biggest single drain. Leave Auto-Brightness on (Settings, Accessibility, Display & Text Size). Turning the screen down helps more than almost anything else.
Weak signal: a phone searching for a mobile signal in a basement, on a train or in a rural area works hard. Where coverage is poor, connecting to Wi-Fi helps.
Location: check Settings, Privacy & Security, Location Services. Set apps to While Using rather than Always unless they genuinely need it, such as a navigation or family-safety app.
Background App Refresh: under Settings, General, Background App Refresh, turn it off for apps that do not need to update while you are not looking at them.
Always On display: on models that have it, an always-on Lock Screen uses some extra power. You can turn it off under Display & Brightness.
Heat: using the phone in direct sun, gaming while charging or keeping it in a hot car drains the battery faster and, over time, ages it.
Streaming and video calls: these are naturally heavy. Downloading music or video over Wi-Fi beforehand uses less than streaming over mobile data.

Low Power Mode

Turn on Low Power Mode from Control Centre or Settings, Battery. It reduces background activity, mail fetching and some visual effects until you charge again. It is the quickest way to get through a long day. Recent iOS versions on some models also offer an adaptive power setting in the same menu, which makes smaller automatic adjustments when your usage is heavier than usual.

Rule out a stuck app or setting

Restart the phone. It clears processes that have got stuck.
Update the problem app, or delete and reinstall it.
If drain is severe and nothing explains it, Reset All Settings (Settings, General, Transfer or Reset iPhone, Reset) resets settings such as Wi-Fi passwords and wallpaper but keeps your data. It fixes some odd cases.

Is it the battery itself?

Batteries wear chemically with age and charge cycles. Go to Settings, Battery, Battery Health (on some models this sits under Battery Health & Charging) to see the Maximum Capacity, a figure compared with when the battery was new. Apple considers a battery worn once it drops below about 80% of its original capacity, and the phone shows a service message when it recommends a replacement. To slow that wear, use Optimized Battery Charging, which holds the charge around 80% overnight and finishes shortly before you usually unplug. On iPhone 15 and later, a charge limit setting lets you cap charging at 80% or another level of your choice, under Settings, Battery, Charging.

When to replace the battery

Maximum Capacity well below 80%, or a service message in Battery Health.
Unexpected shutdowns, especially in the cold or at a high-ish percentage.
The phone needs charging more than once a day despite the fixes above.

A replacement through Apple or an authorised repair provider is usually far cheaper than a new phone and can make an older iPhone feel new again. A swollen battery, one that lifts the screen or bulges the case, needs attention straight away: stop charging the phone and get it seen. What turned out to be draining your battery? Share what you found, or ask about your own phone, in the comments.