iPhone Battery Health: What the Numbers Mean and When to Replace

Your iPhone already knows how worn its battery is. To check battery health on iPhone, open Settings, tap Battery, then tap Battery Health (on iPhone 11, 12, 13 and 14 models the option is called Battery Health & Charging). The screen shows a percentage and a short status message, and the trick is knowing which of those numbers actually matter. Here are the ones Apple publishes, followed by what each means for your phone.

• 80%: the maximum capacity figure behind Apple's battery ratings. Below it, AppleCare+ replaces the battery at no extra charge.
• 500 cycles: how long iPhone 14 models and earlier are designed to keep 80% of original capacity, under ideal conditions.
• 1000 cycles: the same design target for iPhone 15 models and later.
• 100%: the amount of battery you have to use, in total, to complete one charge cycle.
• 80 to 100%: the range for the charge limit on iPhone 15 models and later, adjustable in 5% steps.
• 32° to 95° F (0° to 35° C): the ambient temperature range where iPhone works best.
• 1 year: the Apple Limited Warranty, which does not cover batteries that wear down from normal use.

Where to Find Each Battery Health Number on Your Model

The path is the same starting point on every recent iPhone: Settings, then Battery. What you see after that depends on the model.

On iPhone 15 models and later running iOS 17.4 or later, tap Battery Health. According to Apple's iPhone 11 and later battery page, this screen shows battery health, maximum capacity, whether a replacement is recommended, the cycle count, when the battery was manufactured and when it was first used.

On iPhone 11, 12, 13 and 14 models, tap Battery Health & Charging. You get maximum capacity and peak performance capability, plus the switches for Optimized Battery Charging and Clean Energy Charging. Apple does not list a cycle count on this screen for these models.

What the Maximum Capacity Percentage Measures

Maximum capacity compares your battery's capacity today with what it held when it was new. A brand new phone can read slightly under 100%, because some time passes between when the battery is made and when you activate the phone. That is not a defect.

As lithium ion batteries chemically age, they hold less energy. A phone at 88% simply has about 88% of the fuel tank it started with.

Why 80% Is the Line People Watch

Searches like "iPhone battery health 80" and "battery health at 79" exist for a reason. Apple's battery service page says that with AppleCare+, Apple will replace the battery for no extra charge if its capacity drops below 80%. That makes 80% the practical point where a replacement goes from optional to free for covered phones.

Without AppleCare+, 80% is still a useful signal, but not a deadline. Apple's battery and performance page notes that when health is significantly degraded, the phone shows a message saying an Apple Authorized Service Provider can replace the battery to restore full performance and capacity. Apple also says this message does not indicate a safety issue and the battery can still be used.

So the real question at 79% is whether the phone still gets you through the day. If it does, you can wait. If you are charging at lunch or seeing slowdowns, a new battery is usually the cheapest fix.

500 vs 1000 Cycles: Why Your Model Matters

Apple rates batteries in iPhone 14 models and earlier to keep 80% of their original capacity at 500 complete charge cycles. Batteries in iPhone 15 models and later are rated for 1000 complete charge cycles to hit the same 80% mark. Both figures assume ideal conditions, and Apple adds that the exact capacity depends on how each phone is used and charged.

That doubling matters if you are comparing two phones with the same health reading. An iPhone 14 and an iPhone 16 could both show 90%, but the newer one was designed to wear more slowly from that point on.

What Counts as One Charge Cycle

One cycle is not one trip to the charger. Apple defines a complete cycle as using an amount equal to 100% of your battery's capacity. Use 60% today, recharge overnight, use 40% tomorrow, and together that adds up to one cycle.

Apple also says a complete cycle is normalized between 80% and 100% of original capacity, so the count accounts for the fact that a worn battery holds less. Topping up often doesn't burn through cycles faster; only total usage does.

Peak Performance Capability Messages

The status line under maximum capacity tells you whether the battery can still deliver the bursts of power the phone needs. The healthy message reads that your battery is supporting normal peak performance.

If an older battery causes an unexpected shutdown, you may see a note that performance management has been applied. On iPhone 11 and later, Apple describes performance management as automatic and always on, adjusting in real time. As a battery ages, you might still notice longer app launch times, lower frame rates, dimmer backlight or quieter speakers. In extreme cases, camera features can be temporarily disabled. These are signs the battery, not the phone, is the bottleneck.

The Charge Limit Numbers on iPhone 15 and Later

Apple's charge limit guide explains that on iPhone 15 models and later you can go to Settings, then Battery, then Charging, and pick a limit between 80% and 100% in 5% steps. With the limit set below 100%, the phone charges to within a few points of it and resumes if the level drops more than 5% while plugged in.

Optimized Battery Charging is available only when the limit is 100%. It learns your routine (Apple says it needs at least 14 days and at least 9 charges of 5 hours or more in one location) and delays charging past 80% until shortly before you usually unplug. On iPhone 14 and earlier, you find the switch under Battery Health & Charging.

Temperature Numbers That Protect Capacity

Apple's battery performance tips list 32° to 95° F (0° to 35° C) as the ambient range where iPhone works best. Above 95° F, Apple warns, heat can permanently damage battery capacity, and charging in high heat can damage it further. If your phone gets hot while charging, Apple suggests taking certain cases off.

Worked Example: How Long Until You Hit 80%

Say you use about 60% of your battery on an average day. That is 0.6 cycles per day.

• iPhone 15 or later: 1000 cycles ÷ 0.6 cycles per day = about 1,667 days. Divide by 365 and you get roughly 4.6 years to reach 80% under ideal conditions.
• iPhone 14 or earlier: 500 cycles ÷ 0.6 cycles per day = about 833 days, or roughly 2.3 years.

Now a heavier user who drains 90% daily, which is 0.9 cycles a day:

• iPhone 15 or later: 1000 ÷ 0.9 = about 1,111 days, or roughly 3 years.
• iPhone 14 or earlier: 500 ÷ 0.9 = about 556 days, or roughly 1.5 years.

Real phones rarely follow these lines exactly, but the math gives you a yardstick. If you have an iPhone 15 or later that is two years old, shows 300 cycles and already reads 82%, it is wearing faster than the design target, and it is worth looking at how and where you charge it.

Putting the Numbers to Work

Check your battery health screen every few months rather than every day; the number moves slowly. If you are buying a used phone, ask the seller for a screenshot of this screen, and on iPhone 15 or later look at the cycle count too. Our refurbished iPhone checklist covers what else to inspect, and if you plan to sell, our guide on selling an old iPhone compares fees and payouts. If your phone feels sluggish but the battery reads healthy, the cause is likely elsewhere, so try the tips in how to speed up a slow iPhone.

For more phone and device guides, browse our gadgets section. One last check before booking a repair: confirm whether your phone still has AppleCare+, because below 80%, that coverage can make the replacement free.