How to Check iPhone Battery Health (And the Number Apple Hides)

Your iPhone shows you one number about its battery, and that number is doing a lot of work it was never designed to do. Most guides on how to check iPhone battery health stop at Settings, then Battery, then Battery Health, point at Maximum Capacity, and leave you there. That figure is an estimate. It drifts. On its own it will not tell you whether your battery is genuinely worn out or whether you are about to spend three figures on a repair you did not need.

There is a second number that matters more, and Apple already has it. Your iPhone stores it. Depending on which iPhone you own it either sits two taps away or is buried in a diagnostic log you have to go and dig out yourself.

How to check iPhone battery health in Settings

Open Settings, tap Battery, then tap Battery Health. That is the whole path, and it has not moved in years.

What you get is Maximum Capacity as a percentage, and underneath it a Peak Performance Capability message. Apple's own battery and performance page lists three versions of that message, and they are not interchangeable.

• Supporting normal peak performance. Nothing is being throttled. Whatever the percentage says, iOS is not holding your phone back.
• Unexpected shutdown, performance management applied. This is the one that actually means something. Your battery could not deliver the peak power the phone asked for, the phone cut out, and iOS is now smoothing demand to stop it happening again.
• You have manually disabled performance management. You turned it off after a shutdown. The underlying wear did not go anywhere.

Almost every guide screenshots the percentage and ignores that message. It is the wrong way round. The percentage is a rough gauge of how long you go between charges. The message is the bit that tells you your phone is already misbehaving.

What Maximum Capacity actually measures

Apple describes it as the battery's capacity relative to when it was new. That sounds precise and it is not. It is a modelled figure, calculated from how your battery has been behaving, and iOS revises it as it gathers more data.

That is why the number sometimes sits at 89% for four months and then drops three points in a fortnight, or climbs back up a point after a run of full charge cycles. Nothing broke. The estimate simply got better. If you are checking it daily and reading meaning into single-point moves, you are reading noise.

The number Apple hides on older iPhones: cycle count

Cycle count is the honest number. It is a straight tally, not an estimate, and it maps directly onto how Apple rates the battery in the first place.

Here is the part that trips people up, and the reason so much advice on this is useless. Whether you can see it at all depends on which iPhone you are holding.

iPhone 15 and later: it is right there

On an iPhone 15 or newer running iOS 17.4 or later, Settings, Battery, Battery Health gives you the cycle count, the battery's manufacture date, the date it was first used, and whether Apple reckons a replacement is warranted. Four useful facts, in one screen, and most people have never scrolled far enough to see them.

iPhone 14 and earlier: it is not in Settings at all

There is no cycle count anywhere in Settings on an iPhone 14, 13, 12 or older. Not hidden in a submenu, not behind a toggle. It is simply not exposed. Every video promising the real battery health of your iPhone via the cycle count is, for the majority of iPhones still in use, showing you a screen you do not have.

Two ways round it. The free one is Settings, Privacy and Security, Analytics and Improvements, Analytics Data, then open the most recent log file beginning with Analytics and search it for CycleCount. It is a raw diagnostic log rather than a feature, so treat it as a look under the bonnet, not a supported readout.

The easier route is a desktop tool. Plug the phone into a Mac and something like iMazing or coconutBattery will read the cycle count and the design capacity straight off the device in a couple of seconds. If the number matters enough to go looking, it is worth the two minutes.

One cycle is not one charge

This is where people badly misjudge their own numbers. A cycle is a cumulative 100% of the battery's capacity, not a single plug-in. Charging from 50% to 100% today and 50% to 100% tomorrow is one cycle between them, not two.

So topping up in the car, again at the desk and again on the sofa costs you nothing extra. What costs you is total energy through the cell. Plenty of people who charge constantly and panic about it have lower cycle counts than the friend who runs flat to 5% once a day.

Why 80% is not the line for replacing your battery

The 80% figure has escaped into the wild and lost its meaning on the way. It is a design target, not a warning light. Apple builds the battery to still hold 80% of its original capacity after a stated number of cycles under good conditions. That is a manufacturing promise about durability.

The reason it feels like a threshold is that it doubles as a warranty trigger. If you hold AppleCare, Apple replaces the battery at no extra charge once capacity drops below 80%. That is a commercial line drawn for claims handling. It is not a statement that your phone stops working properly at 79%.

In practice there are two real triggers, and neither is a percentage. The first is that Peak Performance message changing to the unexpected shutdown wording. The second is your own day: if the phone no longer gets you from morning to evening on the usage you have always had, that is the answer, whether it reads 91% or 76%.

500 cycles or 1,000, and what that is in years

This is the single most useful thing on Apple's support pages and almost nobody repeats it. iPhone 14 and earlier are designed to keep 80% capacity after 500 complete charge cycles under ideal conditions. iPhone 15 and later are designed to keep it after 1,000.

Double the rating, same 80% target. Turn that into calendar time and the difference stops being an abstraction. This is my own arithmetic, and it assumes a full cycle's worth of energy every single day, which is heavy use:

• iPhone 14 or earlier: 500 cycles at one a day is about 1 year and 5 months to the 80% mark.
• iPhone 15 or later: 1,000 cycles at one a day is about 2 years and 9 months.
• Same iPhone 15, but a lighter user averaging a cycle every other day: roughly 5 and a half years.

That explains a pattern I hear about constantly. An iPhone 12 or 13 hits the low 80s around its second birthday and its owner assumes something is wrong with it. Nothing is wrong with it. It is doing exactly what it was rated to do. An iPhone 15 in the same hands looks dramatically healthier at the same age purely because the cell is specified to last twice as long.

It also means comparing your percentage against a friend's is close to meaningless unless you are both on the same side of the iPhone 15 line.

What to do when the number really is bad

Say you have checked properly, the shutdown message is showing and the phone genuinely does not last your day. You have four options and they are not equally sensible.

A battery service through Apple is the safe choice and the priciest. Apple's UK repair page quotes battery service per model and adds VAT on top; when I checked this week the pricing table would not render for me at all, so get your own model's figure from Apple before you commit rather than trusting a number from a blog, including this one. Independent UK repairers on the same search sit anywhere from about £20 to about £70, which is a wide enough spread that the cheap end is telling you something about the cell they are fitting.

Buying cover to get a free battery is the option worth doing the maths on before you act. AppleCare One runs at £16.99 a month, which is £203.88 a year by my arithmetic. A single battery service costs less than a year of that, so cover only pays for itself on breakages and multiple devices, never on a battery alone. Buy it because you drop things, not because your capacity reads 78%.

Trading in is where battery health quietly costs you money. Apple's own trade-in grading is fairly blunt about condition, but the resale market is not, and a phone advertised at 84% fetches noticeably less than the same phone at 94%. If you are heading that way, the trade-in quote you get has a clock on it, so check the battery before you start rather than after.

Selling privately usually beats both, and a fresh battery genuinely lifts what you can ask. If you go that route, wipe the phone properly first and leave yourself more time than you think you need.

How to slow the decline without changing how you live

Two settings do most of the work and both are on the same Battery screen you just opened. Optimised Battery Charging holds the phone at 80% overnight and finishes the last stretch shortly before you normally wake. On newer iPhones there is also a hard charge limit you can set, which caps the phone below 100% permanently.

Heat does more damage than charging habits ever will. A phone left on a car dashboard in July, or gaming while fast charging, is a worse day for the cell than a week of plugging it in whenever you fancy. If you only change one thing, take the case off when it is running hot and charging.

Frequently asked questions

Why can't I see battery cycle count on my iPhone?

Because you are almost certainly on an iPhone 14 or older. Cycle count only appears in Settings on iPhone 15 and later running iOS 17.4 or newer. On earlier models it exists on the device but is not surfaced anywhere in Settings, so you need the Analytics Data log or a desktop tool to read it.

Is 85% battery health bad?

No, and on an iPhone 14 or earlier at two years old it is completely ordinary. What matters is whether the Peak Performance message still says normal and whether the phone lasts your day. If both are fine, 85% is a number, not a problem.

Does replacing the battery reset Maximum Capacity to 100%?

With a genuine Apple battery fitted by Apple or an authorised provider, yes, it should read 100% and the cycle count starts again. A third-party cell often will not report properly, and you may see an unknown part or service warning instead, which is worth weighing against the lower price.

My take

Check the message, not the percentage. If it says your battery supports normal peak performance and the phone still gets you through the day, do nothing, whatever the number is. If it mentions an unexpected shutdown, book the battery service and stop agonising, because that is your phone telling you plainly rather than estimating.

And if you are on an iPhone 15 or later and quietly worried that yours is ageing badly, go and look at the cycle count before you spend anything. Half the people I say that to find they are barely a third of the way through what the battery was rated for.

Source: iPhone battery and performance, Apple Support