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This battery health calculator divides your laptop battery’s full charge capacity by its design capacity to show how much of its original capacity is left, how worn it is, and whether it’s time to think about a replacement. On Windows 11 you get both numbers from the powercfg /batteryreport command.
It runs in your browser: nothing is uploaded.
How to use the battery health calculator
- Get two numbers for your battery: the design capacity (what it held when new) and the full charge capacity (what it holds now). On Windows 11 both are in the battery report; the steps are further down this page.
- Type the first number into Design capacity (mWh) and the second into Full charge capacity (mWh). Use digits only, without spaces, commas or the unit.
- Prefer not to copy numbers by hand? Open Or paste your battery report and paste the text of the Installed batteries section from battery-report.html into the box. The tool picks out the two capacities for you.
- Select Check battery health.
- Read your health percentage, the wear percentage and the verdict. The sections below explain what each one means and what to do next.
If your laptop has two batteries, the report lists each one separately. Check them one at a time.
How the battery health calculator works
The maths is one division. Health = full charge capacity ÷ design capacity × 100. Wear is the rest: wear = 100 − health. Design capacity is the energy the manufacturer rated the battery for when it was new. Full charge capacity is what the battery’s own monitoring chip estimates it can hold today.
Take the example numbers shown in the empty fields: a design capacity of 57,000 mWh and a full charge capacity of 49,500 mWh. 49,500 ÷ 57,000 = 0.868, so the battery has about 86.8% health and 13.2% wear. It can still hold most of its original charge, so it gets a Good verdict.
Windows reports capacity in milliwatt-hours (mWh), which is why the fields say mWh. Phones and some diagnostic apps use milliamp-hours (mAh) instead. The ratio still works as long as both numbers use the same unit, so you can enter mAh values too. Don’t mix the two.
How to read your result
| Health | Verdict | What it means | What to do |
|---|---|---|---|
| 80% or more | Good | The battery still holds most of its original charge. | Nothing. Check again in six months or so. |
| 60–79% | Fair | Noticeably shorter battery life than when new. | Consider a replacement soon, especially if you work unplugged. |
| Below 60% | Replace | The battery has lost a large share of its capacity. | Plan a replacement; ask the manufacturer or an authorised repairer. |
The 80% line isn’t arbitrary. Apple says its Mac laptop batteries are designed to keep up to 80% of their original capacity at their maximum cycle count, and Google recommends replacing a Pixel battery once it falls below 80%. Below that point, most people start to notice the shorter runtime.
A brand-new battery can show slightly more than 100%. That’s normal: the design figure is a minimum rating, and the estimate settles down after a few charge cycles.
Whatever the number says, stop using a laptop whose battery is swelling: the case bulges, the trackpad lifts or the lid no longer closes flat. Unplug it, don’t charge it, and get it serviced.
Before you send a laptop away for a battery swap, back up your Windows PC in case the repair shop resets it. If the battery is only one of several problems, it may be time to check whether your PC can run Windows 11 or whether a new laptop makes more sense.
How to check laptop battery health on Windows 11 with powercfg
Windows 11 has a built-in battery report that lists both numbers the calculator needs. Microsoft documents it as part of the powercfg tool: running powercfg /batteryreport saves an HTML report in the folder the command runs in.
- Right-click the Start button and choose Terminal. Command Prompt works too.
- Type
powercfg /batteryreportand press Enter. - Windows replies with the full path of the saved file, usually C:\Users\YourName\battery-report.html.
- Open File Explorer, go to that folder and double-click battery-report.html. It opens in your web browser.
- Scroll to Installed batteries. Note the DESIGN CAPACITY and FULL CHARGE CAPACITY values, then enter them in the calculator above, or copy the whole section into the paste box.
The same section shows the CYCLE COUNT: how many full charge-and-discharge cycles the battery has been through, if the laptop reports it. Further down, Battery capacity history shows how full charge capacity has changed over time, which tells you whether wear is steady or suddenly speeding up.
More Windows guides are on our Windows hub, including Windows 11 settings worth changing.
How to check battery health on a Mac (based on Apple’s documentation)
A Mac does the maths for you. Based on Apple’s support pages, choose Apple menu → System Settings → Battery and look at Battery Health. It shows Normal or Service Recommended. Select the info button next to it for more detail, including Maximum Capacity on recent macOS versions.
For the cycle count, hold Option, click the Apple menu, choose System Information, then select Power under Hardware. Apple rates current MacBook Air and MacBook Pro batteries for 1,000 cycles.
How to check battery health on Android (based on Google’s and Samsung’s documentation)
Not every Android phone shows battery health, and the menus differ by brand.
- Google Pixel 8a and later: according to Google, go to Settings → Battery → Battery health. The status reads Normal or Reduced (below 80%), and Battery capacity shows the estimated percentage. Earlier Pixels don’t show the status.
- Samsung Galaxy: Samsung’s support pages point to the Samsung Members app: open Phone diagnostics and run Battery status. Recent One UI versions also show capacity and cycle count under Settings → Battery → Battery information on some models.
- Other Android phones: look in Settings → Battery or the maker’s support app. If you only see design and current capacity in mAh, enter both numbers in the calculator.
If your phone’s battery drains fast after an update, the cause is often settings rather than wear: see One UI 9 battery drain settings to check, and more on our Android hub.
Limitations
- The result is only as good as the numbers. Full charge capacity is the battery chip’s estimate, and it can drift until the battery goes through a few full cycles.
- Health measures capacity only. It can’t detect swelling, a failing cell or a battery that shuts the laptop down under heavy load.
- Some replacement batteries report an odd design capacity, such as zero or the same value as full charge, which makes the result meaningless.
- The verdict bands are a rule of thumb. A battery at 75% may be fine if you mostly work plugged in, and replacement advice from your laptop’s manufacturer comes first.
- Desktop PCs have no battery, so there’s nothing to check.
FAQ
What is a good battery health percentage for a laptop?
80% or more is good. Apple and Google both use 80% as the point where a battery is considered worn, and most people start to notice shorter battery life below it.
How do I check my laptop battery health on Windows 11?
Open Terminal or Command Prompt, run powercfg /batteryreport, open the battery-report.html file it saves, and compare FULL CHARGE CAPACITY with DESIGN CAPACITY under Installed batteries, or enter both in the calculator.
Is 70% battery health bad?
It’s not dangerous, but the battery holds about 30% less than when it was new, so you’ll get noticeably less time unplugged. The calculator rates it Fair: consider a replacement soon if battery life matters to you.
Can battery health be restored?
No. Capacity loss comes from chemical ageing and is permanent. A few full charge cycles can correct a wrong estimate, but they don’t bring lost capacity back.
How many charge cycles does a laptop battery last?
It depends on the manufacturer. Apple rates current MacBook batteries for 1,000 cycles; check your laptop maker’s support pages for its rating.