Your phone used to last the whole day. Now it hits 20% by dinner, even though you charge it the same way you always have. The battery icon still fills to 100% every morning, so nothing looks broken — but a full charge no longer means a full battery. That is exactly what battery health measures: how much charge your battery can still hold compared with when it was new.
This guide covers what the numbers mean, the exact steps for iPhone, Pixel and Samsung, what to do when your phone shows no reading at all, and when a battery is actually worth replacing.
What battery health actually measures
Battery health is not the percentage in your status bar. That number is the charge level — how full the battery is right now. Battery health is the capacity: how much energy a full charge holds compared with a brand-new battery.
A battery at 85% health that shows 100% charged holds about 85% of the energy it held on day one. That is why the phone dies earlier even though "it charged to 100%". Every lithium-ion battery loses capacity as it chemically ages, and every full discharge-and-recharge counts toward that wear — one charge cycle means using an amount of charge equal to 100% of the battery's capacity, whether in one go or spread over several days. Charging from 100% to 50% and back to 100% is half a cycle, not one.
Check battery health on iPhone
Apple gives iPhone owners the clearest built-in reading of any phone. The exact screen name depends on your model.
On iPhone 15 and later:
- Open the Settings app.
- Tap Battery.
- Tap Battery Health.
- Read Maximum Capacity, Cycle Count, the manufacture date and the date of first use.
On iPhone 14 and earlier:
- Open the Settings app.
- Tap Battery.
- Tap Battery Health & Charging.
- Read Maximum Capacity and the message under Peak Performance Capability.
Apple's own iPhone battery health guide lists the same paths and says the screen shows your battery's capacity, peak performance, and whether it needs to be serviced. On a healthy battery, Peak Performance Capability says the battery is currently supporting normal peak performance. If the battery has degraded badly, iOS may apply performance management and say so here — and if the screen shows Service, Apple recommends considering a replacement.
Apple designs iPhone 14 models and earlier to retain 80% of their original capacity at 500 complete charge cycles under ideal conditions, and iPhone 15 models at 1,000 complete charge cycles — confirmed on Apple's own batteries service and recycling page. Real results depend on how you use and charge the phone, so treat these as design targets, not guarantees.
Check battery health on Google Pixel
Pixel phones got a proper battery health screen with Android 16, but only on newer models — so check which Pixel you own first.
On Pixel 8a and later:
- Open the Settings app.
- Tap Battery, then Battery health.
- Read the status: Normal or Reduced. Tap Battery capacity on the same screen for the estimated percentage.
- For the cycle count, go to Settings > About phone > Battery information — the same screen also shows the manufacture date and the date of first use.
Google's own Pixel battery guide confirms these paths and explains the statuses: Normal means capacity is within normal limits, Reduced means it has fallen below 80% — and when it is Reduced, Google recommends replacing the battery. Unavailable means the phone cannot determine the status yet.
Google rates Pixel 8a and later batteries to keep up to 80% capacity for about 1,000 charge cycles, and Pixel 3 through Pixel 8 Pro and Pixel Fold batteries for about 800 cycles. Google also notes the first health values are based on lab results and may differ from the battery's actual state, and that capacity is estimated by the battery's fuel gauge — so treat the percentage as an estimate, not a laboratory measurement.
Check battery health on Samsung Galaxy
Samsung does not put a health percentage in Settings on most Galaxy phones. Instead it offers a diagnostic test in its own app, and on newer models a battery information page.
With the Samsung Members app (the method Samsung documents):
- Open the Samsung Members app.
- Tap the Support tab.
- Tap Get Started under Phone diagnostics.
- Once the diagnostic is complete, tap the Battery status icon.
- Read the result.
Samsung's own Galaxy battery status guide lists exactly these steps and the three possible results: Normal means no issues with the battery, Weak means efficiency may have decreased through use or environmental conditions, and Bad means battery life has significantly degraded and you should visit a Samsung Support Centre for advice.
On newer Galaxy phones, also check Settings:
- Open Settings.
- Tap Battery.
- Scroll down and tap Battery information.
This page shows the battery status, level and typical capacity in mAh. Guides that tested recent Galaxy phones report that it shows no health percentage and no cycle count on some models — so if yours shows no percentage, the Samsung Members result is the reading that actually judges the battery's condition.
What to do when your phone shows no health reading
Most Android phones outside the Pixel 8a-and-later range and recent Galaxy models have no built-in battery health figure. That does not mean you cannot check — it means the phone will not tell you itself.
| Phone | Where to check | What you get | Replace when |
|---|---|---|---|
| iPhone | Settings > Battery > Battery Health (15+) or Battery Health & Charging (14-) | Maximum Capacity %, cycle count (15+), Peak Performance Capability | Below 80%, or a "Service" message |
| Pixel 8a and later | Settings > Battery > Battery health; cycle count at Settings > About phone > Battery information | Normal / Reduced status + estimated capacity % | Reduced (below 80%) or about 1,000 cycles |
| Samsung Galaxy | Samsung Members > Support > Phone diagnostics > Battery status | Normal / Weak / Bad | "Bad", or "Weak" with fast drain |
| Other Android | No built-in reading on most models | Estimate from a battery app (see below) | About 80% estimated capacity, plus symptoms |
Use a battery-monitoring app. The best-known option is AccuBattery: install it, use the phone normally for several charge cycles, and it estimates health in mAh and as a percentage from your actual charging sessions. The first reading is rough and improves as it collects more cycles — so do not judge the battery on day one, and treat the result as an estimate, not a manufacturer measurement.
Skip the dialer code on modern phones. The old `*#*#4636#*#*` code opens a hidden Testing menu on some phones, but on most modern phones the Battery information page is gone from that menu — it shows only charge level, temperature and voltage, if anything. It is not a reliable health check any more.
When to replace the battery
A number alone rarely settles it. Replace the battery when the reading and the symptoms agree:
- Maximum Capacity below 80% on iPhone, a Reduced status on Pixel, or a Bad result on Samsung — these are the manufacturers' own replacement lines.
- Cycle count past the rated life — about 500 cycles on iPhone 14 and earlier, 1,000 on iPhone 15 and later and Pixel 8a and later, 800 on older Pixels — even if the percentage still looks acceptable.
- Symptoms that match the reading: the phone dies at 20–30%, shuts down in the cold, charges much faster than it used to, or the battery drains noticeably faster than the same model did when new.
- A "Service" message on iPhone, or the phone applying performance management to stay stable.
If the percentage is in the high 80s or 90s and the phone still lasts the day, there is nothing to fix — keep using it and re-check in a few months. A battery replacement is a repair, not maintenance, and it is cheapest through the manufacturer or an authorized service provider, who can also confirm the reading before you pay.
Slow down battery wear from here
You cannot reverse the capacity you have already lost, but you can slow the rest of the decline. The two factors every manufacturer names are heat and charging habits.
- Keep the phone cool while charging. Google recommends charging at about 25°C (78°F) with a compatible USB-C PD or PPS charger, and avoiding prolonged exposure above 35°C (95°F). A phone baking on a car dashboard or under a pillow ages faster than one charged on a desk.
- Cap the charge at 80% when you can. On iPhone, turn on Optimized Battery Charging or the 80% Charge Limit in the Battery Health screen. On Pixel, use Settings > Battery > Battery health > Charging optimization and choose Adaptive Charging or Limit to 80%. Our guide to limiting charging to 80% on iPhone, Pixel and Samsung walks through the exact settings on all three.
- Avoid storing a dead phone. If you will not use the phone for more than 30 days, Google recommends storing it with at least 50% charge.
- Do not chase the percentage daily. Battery health moves slowly — checking once every few months is enough. A single-point drop after an update is usually the estimate recalibrating, not sudden damage.
FAQ
What is a good battery health percentage?
Anything in the high 90s behaves like new, the mid-to-high 80s is normal wear on a phone that is a year or two old, and below 80% is the line Apple, Google and Samsung all use as the point to plan a replacement. The percentage matters less than the trend: a slow, steady decline is normal, while a sudden drop after damage or heavy heat exposure is worth investigating.
Does 80% battery health mean I need a new battery?
Not immediately. 80% is where the manufacturers' design targets end and where a free replacement under AppleCare+ or a Pixel replacement recommendation begins — but a phone at 79% that still lasts your day is fine to keep using. Replace it when the short runtime starts affecting you, the phone shuts down early, or the screen shows a Service or Reduced warning.
Why does my Android phone not show battery health?
Because most Android makers never built the screen. Google only added a Battery health page for Pixel 8a and later, and Samsung judges battery condition through the Samsung Members diagnostic instead of a percentage. On any other Android phone there is no built-in reading — use a battery-monitoring app such as AccuBattery for an estimate, or check whether your maker added a Battery information page in a recent update.
Can I check battery health without installing an app?
Yes, on iPhone, Pixel 8a and later, and Samsung Galaxy — all three have a built-in check described above, and none of them needs a download. On other Android phones there is no built-in option, so an app is the only way to get an estimate without a repair shop's diagnostic tools.
Does checking battery health drain the battery?
No. Reading the Battery Health screen costs nothing measurable — it only displays a figure the phone already tracks. Battery-monitoring apps do use a small amount of power while they record charging sessions, but the drain is tiny compared with the screen or a single app.
Is the AccuBattery estimate accurate?
It is a good estimate, not a manufacturer measurement. It learns your battery's real capacity from several full charge sessions, so it gets more accurate over the first week or two of use. Treat its percentage as a guide — if it says 82% and the phone dies early, trust the symptoms over the number, and the other way round.