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Laptop battery health check

See how much of its original charge your laptop battery still holds, and whether to replace it. Windows: run one command and drop in the file. Mac or Chromebook: type in the health percentage.

Battery health check

Runs in your browser · nothing uploaded
  1. Right-click the Start button and open Terminal, not the Admin one (or search for cmd and open Command Prompt).
  2. Paste this and press Enter:
    powercfg /batteryreport
  3. Windows saves battery-report.html in your user folder. Drop it below. In the file picker you can paste %USERPROFILE%\battery-report.html into the File name box. Or copy the path Windows prints after the command. (As admin, it saves to C:\Windows\System32.)

The report is read in this tab and never leaves your computer. It includes your computer’s name; we don’t see it.

What the numbers mean

Battery health is the full charge capacity divided by the design capacity. Design capacity is what the battery held the day it was made. Full charge capacity is what it holds today. A battery that was 86 Wh new and now fills to 66.9 Wh is at 78%.

The cycle count is how many full charges' worth the battery has been through. Two days of draining from 100% to 50% count as one cycle. Wear tracks cycles, heat and time spent sitting at 100%, so two laptops with the same count can be in different shape.

HealthVerdictWhat to do
Over 110%Can't judgeThe design capacity the battery reports is wrong, often on a non-original replacement. Judge it by runtime.
101 to 110%As newNothing. New batteries often read a little high until the gauge settles.
90 to 100%HealthyNothing.
80 to 89%Normal wearKeep using it. It's still above the line most makers rate batteries to.
70 to 79%WornReplace it when the shorter runtime starts to get in your way.
60 to 69%Replace soonPlan a replacement. Worn batteries can shut down early under load.
Under 60%ReplaceReplace it, and check for swelling first.

The 80% line: Apple designs MacBook batteries to keep up to 80% of their original capacity at their rated cycle count, 1,000 for recent models (Apple, checked Oct 24, 2026). Windows laptop makers set their own ratings; check your maker's battery spec.

Why Windows doesn't just show you a percentage

Windows Settings shows charge level and which apps use power, but on most laptops it doesn't show how worn the battery is. The numbers are there. They're just in the battery report, a page of tables that powercfg /batteryreport writes to your user folder (Microsoft documents the command on its powercfg page).

The checker reads three things from that report: the design and full charge capacity of each battery, the cycle count, and the capacity history Windows has logged since it was installed. If the history covers a few months, it also works out how fast the battery is wearing and roughly when it will cross 80%. Some laptops report the cycle count as a dash; that's the battery not passing it to Windows, not a fault.

If Windows lists a battery but leaves the design capacity blank, the checker can't work out health from the report. Your maker's app (MyASUS, HP Support Assistant, Lenovo Vantage or Dell SupportAssist) may show both capacities, and you can type them into the checker.

Laptops with two batteries, like some ThinkPads, get one verdict for both together and a line for each.

Checking a Chromebook

Open the Diagnostics app. Select the time at the bottom right, then Settings, About ChromeOS, Diagnostics, or search the launcher for Diagnostics. The Battery section shows battery health and the cycle count (Google documents the app on its Chromebook help pages). Pick Chromebook on the checker's Mac or Chromebook tab and type both in.

My laptop dies in an hour: battery or something else?

If health is 80% or more, the battery is rarely the problem. Short runtime then comes from power use: a bright screen, apps running in the background, or a performance power mode. On Windows, Settings › System › Power & battery shows battery use per app, and the Power mode setting there has a Best power efficiency option (Microsoft).

Below 70%, the battery is the likely cause. A new battery usually costs far less than a new laptop, but get a quote first: many are glued in or need the case opened. Our repair or replace check helps you weigh the quote against the laptop's age.

When to replace a laptop battery

Replace it when the runtime no longer covers your day, or at once if it's swelling. Health alone doesn't force the decision. A laptop at 75% that lives on a desk is fine; the same laptop on a student's backpack schedule might not be.

Swelling is the one case that can't wait. Look for a trackpad that has lifted or stopped clicking, a case that rocks on a flat table, or a gap along the bottom panel. If you see any of those, unplug the laptop, stop charging it and get the battery replaced.

Before you buy a replacement, match the part number printed on the old battery. The checker shows the name Windows reads from the battery when it looks like a part number; names like "Primary" or ASUS's "BIF0_9" aren't. Your maker's parts store or an authorized repair shop is the safest place to buy. Dell, for one, says third-party batteries carry more reliability and safety risk and aren't covered by its warranty. If you buy elsewhere, match the part number, voltage and Wh. On a MacBook, battery service goes through Apple or an Apple Authorized Service Provider.

Apple says a battery can keep working past its rated cycle count, though you may notice shorter battery life, and it recommends a replacement once the count is reached.

Questions people ask

Is it safe to upload my battery report here?

Nothing is uploaded. The checker reads the file inside your browser tab and never sends it anywhere. The report does include your computer's name and the battery's serial number, so don't post it publicly elsewhere.

Is 85% battery health bad?

No. 85% is normal wear for a laptop that's a year or two old. Most makers treat 80% as the point where a battery has used up its rated life, and you're above it.

Can battery health go back up?

A little, sometimes. The capacity reading is an estimate, and it can jump a few points after the gauge recalibrates. A battery doesn't regain capacity it has really lost.

Does leaving my laptop plugged in wear the battery?

Sitting at 100% all day speeds up wear. Many laptops let you cap the charge: Lenovo Vantage, MyASUS and Dell's battery settings have options for it, and macOS has Optimized Battery Charging. Turn it on if the laptop lives on a charger.

How do I check the battery on a used laptop before I buy it?

Ask the seller to run the command, then double-click battery-report.html to open it on their laptop. Type the design and full charge capacity into the checker on your phone, and check that the report time at the top is today. A cycle count under about 20 on a laptop that's a few years old usually means the battery has been replaced; that's our rule of thumb, so ask what was fitted.

I can't find battery-report.html. Where did it go?

Windows prints the full path it saved to right after the command runs, so copy it from there. If you opened Terminal as admin, the file lands in C:\Windows\System32 instead of your user folder.

Why does my report show no battery?

Desktops have none. On a laptop, it means Windows can't see the battery at all, which points to a dead battery, a loose connector or a firmware problem. That's one for a repair shop.

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