All tools
Which tool do I need?
| Your question | Use |
|---|---|
| How healthy is my battery? | Battery health checker |
| How long will my battery last? | Battery life calculator |
| Is this replacement battery the same size as mine? | mAh ↔ Wh converter |
| Can I fly with this battery? | mAh ↔ Wh converter |
| Why does my battery go down while plugged in? | Charger wattage checker |
| Is a smaller or USB-C charger enough? | Charger wattage checker |
Where the numbers come from
Every tool uses values that Windows already records. Open Command Prompt, run powercfg /batteryreport and open the battery-report.html file it saves. You'll find:
- Design Capacity and Full Charge Capacity in the Installed batteries section, used by the checker, the calculator and the converter.
- Energy drained and Duration in the Battery usage section, which give your laptop's real power draw in watts for the calculator and the charger checker.
Step-by-step instructions are in the Windows 11 guide and the Windows 10 guide. To see how these numbers look on real laptops, browse our real battery report data.
Privacy
All four tools run entirely in your browser with JavaScript. Your battery report and the numbers you type are not sent to our server or stored.
Senior software engineer in Karachi with more than five years of experience building web applications in ASP.NET Core, C# and JavaScript. He built the free battery health checker and these calculators, and checks them against Microsoft and laptop makers’ documentation and real battery reports.