How to Check a Laptop's Battery Health (Windows and macOS)
Battery health is the one thing you can't judge from photos. Here's how to check it yourself on Windows with a built-in battery report, and on a MacBook with System Information — and how to read the numbers.
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- RenewByte Team
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- 6 min read
A laptop battery wears out gradually. Every charge cycle reduces the amount of energy it can hold, so a two-year-old battery that once lasted eight hours might now last five. When you're buying a refurbished or second-hand laptop — or just wondering why your own laptop dies sooner than it used to — checking battery health takes a few minutes and needs no extra software.
The two numbers that matter
Whatever operating system you use, battery health comes down to two figures:
- Design capacity — how much energy the battery could hold when it was new, measured in milliwatt-hours (mWh) or milliamp-hours (mAh).
- Full charge capacity — how much it can hold today.
Divide the second by the first and multiply by 100 and you get battery health as a percentage:
Battery health (%) = Full charge capacity ÷ Design capacity × 100
For example, a battery designed for 50,000 mWh that now charges to 42,000 mWh is at 84% health.
A third number, cycle count, tells you how many full charge cycles the battery has been through. Two half-charges count as roughly one cycle.
On Windows: generate a battery report
Windows includes a built-in tool that produces a detailed battery report.
Press the Start button, type cmd, then right-click Command Prompt and choose Run as administrator. (PowerShell or Windows Terminal work too.)
Type the following command and press Enter:
powercfg /batteryreportWindows prints the location of the saved file — usually something like
C:\Windows\system32\battery-report.htmlor your user folder. To choose the location yourself, run:powercfg /batteryreport /output "C:\battery-report.html"Open that HTML file in any browser.
Reading the Windows report
Scroll to the Installed batteries section. You'll see:
- DESIGN CAPACITY — the original capacity.
- FULL CHARGE CAPACITY — the current maximum.
- CYCLE COUNT — shown on most laptops, although some models report it as blank.
Further down, Battery capacity history shows how full-charge capacity has changed over time, and Battery life estimates shows how long the battery has actually lasted based on recent usage — often the most practical number of all.
Some manufacturers also include their own tools: Lenovo Vantage, Dell's power management apps and HP's support utilities show battery health and let you run a battery test.
On a MacBook: System Information
macOS shows battery details in two places.
Quick check
Open System Settings → Battery. Next to Battery Health, click the ⓘ button. You'll see a condition (such as Normal) and, on recent macOS versions, a Maximum Capacity percentage.
Detailed check (with cycle count)
- Hold the Option key and click the Apple menu, then choose System Information. (Or open System Settings → General → About and click System Report.)
- In the sidebar, under Hardware, select Power.
- Under Health Information, note the Cycle Count, Condition and, on newer macOS versions, Maximum Capacity.
Apple publishes the rated maximum cycle count for each MacBook model on its support website — for most recent models it is 1,000 cycles. The Condition field will read Service Recommended if macOS detects the battery is significantly degraded.
How to interpret the results
There isn't a single cut-off, but these rough guidelines help:
| Battery health | What it usually means |
|---|---|
| 90% and above | Close to new — you'll barely notice any difference |
| 80–89% | Normal wear for a used battery; still good for daily use |
| 70–79% | Noticeably shorter runtime; fine if you're usually near a plug |
| Below 70% | Consider a replacement if you rely on battery life |
Runtime also depends on the laptop itself — screen brightness, processor and what you're doing — so two laptops with the same health percentage can last different amounts of time.
Why this matters when buying refurbished
Battery health is the component that varies most between refurbished laptops of the same model. A good listing should tell you the measured battery health, not just "battery working". Every laptop we sell has its battery health measured and recorded during our quality testing, and the figure is shown on the product page.
It's also worth checking the laptop yourself when it arrives, using the steps above. If something doesn't match the listing, our warranty and returns policies explain what to do.
Keep your battery healthy for longer
- Avoid heat. High temperatures age lithium-ion batteries fastest. Don't leave a laptop in a hot car or use it on a bed or pillow that blocks the vents.
- Don't keep it at 100% all the time. If your laptop is always plugged in, use the charge-limit feature many manufacturers offer (for example in Lenovo Vantage, Dell's power settings or HP's BIOS battery options), or macOS's Optimised Battery Charging.
- Avoid regular deep discharges. Running the battery to 0% often adds unnecessary wear.
- Use a good-quality charger that matches your laptop's rated wattage.
For more habits that keep a laptop running well, read our laptop maintenance tips.
