Technology Explained

Use This Formula to Estimate the Battery Life of Any Laptop

Dan Price 21-03-2018

It’s not easy to establish the true battery life of a laptop—at least not without using it.


Manufacturers aren’t exactly honest in their advertising, and the facts are obfuscated behind all sorts of numbers and technical jargon. For someone who spends a lot of time on the road, that lack of transparency can quickly become problematic.

For example, if poor battery life is a deal-break when you’re buying a new machine The Best Laptops Under $1,000 Looking for the best laptops under $1,000? We've rounded up a range of Chromebooks, Windows 10 laptops, and macOS Ultrabooks -- all under a thousand bucks. Read More , how are you supposed to make an informed decision? You don’t want to be forced to constantly take battery saving measures How to Save Battery Life in Windows 10 With Power Throttling Microsoft introduced power throttling which gives Windows users more control over how individual apps handle battery consumption while running in the background. Read More just because a manufacturer conned you.

Luckily, you can take matters into your own hands—you just need a special math formula (and possibly a calculator).

The Formula for Estimating Laptop Battery Life

Just divide your computer battery’s watt-hours by your estimated wattage. The result is the number of hours you can expect your battery to last.

Your expected wattage varies depending on the task you’re performing. Gaming will use between 40 and 60 watts, watching video will consume 15 to 30 watts, and web browsing will eat 10 to 15 watts.


The watt-hours of your battery can be found on the battery itself, on the manufacturer’s website, or on the accompanying spec sheets.

You can also find the information using the operating system. On Windows, open Command Prompt, type powercfg /batteryreport, head to the path it spits out, and open battery-report.html in your browser. On Mac, hold Option, then navigate to Apple > System information > Hardware > Power.

Remember, all batteries degrade over time, so this calculation is only going to be accurate on relatively new devices. If you’re not getting the amount of usage out of your battery as you think you should be, check out our guide to troubleshooting battery issues on Windows and Mac Learn These Tips to Solve Battery Issues on Apple and Windows Devices Here are two resources that will help you tackle your battery woes on Apple devices and Windows machines. Read More .

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  1. Rohit
    March 22, 2018 at 5:07 am

    Nice Article. I don't find any website for hindi stories though but recently got which is having good collection of both hindi and english stories just like the above story websites.