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How long does your laptop last on a charge? Here’s how to find out

Battery life is  always variable, and the way hardware manufacturers state an official length for laptop battery life as if it’s written in stone doesn’t help. earning to monitor laptop battery life is essential — it’s the difference between finishing that report over coffee or kicking yourself because you didn’t bring your power cord.

Luckily, there are a few ways you can get an accurate measure of battery life, not just for your model of laptop, but for your specific machine and your usage habits. Follow the steps below for some easy-to-use methods.

Related: Work that battery magic with these 11 tricks and tips to extend your laptop battery

Battery settings

Before we start, make sure your power plan is configured exactly how you want it. Windows works hard to last long at the default settings, but if you’d like to tweak it to your particular usage, you can. In Windows 7 and later, the tool you’re looking for is “Power Options” — just use the Start button or Windows button, then search for “power options” and click the first result.

battery settings
Michael Crider/Digital Trends

You’ll see two plans by default — Balanced and Power Saver. Click on “Change plan settings” next to either one to adjust it, or click “create a power plan” to make a new one. You can switch between plans at any time. The next screen gives you basic options for what happens when your computer is plugged in or on battery power; obviously we’re interested in the latter.

In the main screen you can change how bright the display is, when the display turns off (without user input, that is), and how long it waits to go to sleep. Those are standard options, but if you really want to customize things, click “change advanced power settings.” This menu will let you change much more. Pay specific attention to the “Battery” section — it allows you to tweak when various alerts and changes happen. When you’re finished, click “OK,” then “Save changes.”

The basics

Of course the simplest way to get measure of battery life is to time yourself as you use your laptop. Windows’ built-in battery estimate isn’t much help — it’s only a guess, and it will go up and down as you use your machine in different ways. For the simplest solution, use a stopwatch or a stopwatch app (the default clock app on Android and iOS includes a stopwatch), making sure to start as you begin using your laptop with a full battery. Stop the watch whenever you turn off the machine or put it to “sleep,” and see how long it lasts.

For the best results, use your laptop as you do most regularly, like during a full day of work. You’re not looking to see the maximum theoretical battery life, you’re looking for a good metric of how long it will last while you use it.

For the best results, make several tests and average them together. This is a pretty good basic number for how long your laptop will last under typical use. You can test under multiple conditions, for example, while watching a looped video or playing a taxing game. If you won’t be actively using your laptop while you test, be sure to set the “put the computer to sleep” parameter in Power Options to “Never” (see above).

Let’s get technical

Windows 8 and Windows 10 have a built-in battery meter that most users don’t know about, and it will allow you to get exact times for when your laptop is at full power and when it finally shuts down. Press the Windows button and the R key at the same time to open up the Run command, then type “cmd” and press Enter to open Command Prompt.

Type the following into Command Prompt exactly and press Enter:

powercfg /batteryreport

cmd battery
Michael Crider/Digital Trends

Now open File Explorer and navigate to your user folder at C:/Users/[your username]. Inside you’ll find an HTML file labeled “battery-report.” Double-click the file and it will open in your default web browser.

This report is invaluable. It tells you all kinds of interesting hardware information about your laptop’s battery (or even batteries, if your machine has more than one). You can comb through a ton of data here, but what you’re looking for is “Recent usage.” This is an exact record of your battery level and the times at which it was recorded, making a new entry whenever your power cord is attached, or when the computer is turned off or put to sleep.

recent usage power report
Michael Crider/Digital Trends

You can use this method to get a precise recording of your battery level whenever you like. It’s quite handy. Again, to get an accurate general reading, it’s best to take several tests and average them together.

Battery health

Over time, your computer’s battery will begin to lose life. There’s no way around it — it’s just an unfortunate physical limitation of the technology. Aside from general measurement, you can check the Capacity section in the power report to see exact miliwatt-hour (mWh) values at different percentages. Compare these values with the official capacity in your battery manufacturer’s specifications to see if you need to replace your battery — or your entire machine, if the battery is sealed. This is a good time to check and see if it’s still under warranty.

Related: Three years of laptop battery life explored

Other tools

If you’d like to do even more to measure your battery life, there are third-party programs that will automate the process. These will be precise measurements under strict conditions, and will allow you to gauge your battery life versus other hardware that’s taken an identical test, but it’s generally less useful than the more personal methods mentioned above. Battery Eater is a popular (and free) third-party tool that accomplishes this, but you can also run the Futuremark Peacekeeper web-based battery tool in any modern browser.