Your laptop keeps track of how much its battery has worn down since you first started using it.
You can find out your battery’s health in about a minute on both Windows and Mac, and you don’t need to install anything.
Most owners never check this number, but it’s one of the first things an inspection will look at. It’s good to know it before someone else does.
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Disclosure: Cashkr is our own device buyback service. We buy used laptops, so we have an interest in you selling one. The checks below are built into your laptop and have nothing to do with us.
Rabin Khadka covers smartphones, laptops and India’s growing market for used devices. She spends most of her time tracking launch prices, price drops and resale values, and has a particular interest in why two phones that cost the same on launch day can be worth very different amounts two years later.
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Windows can create a full battery report for you. This tool is built in and completely free.
Click Start, type cmd, and open Command Prompt.
Type this and press Enter:
powercfg /batteryreport
Windows will tell you where it saved the file. Just open that file in your browser.
Microsoft describes the command as generating "a report of battery usage characteristics over the lifetime of the system", and says that running it "generates an HTML report file in the current path".
Scroll down to the section called Installed batteries. There are two important lines to look for.
Design Capacity. What the battery held when it was new.
Full Charge Capacity. What it holds now, fully charged.
Divide the full charge capacity by the design capacity. This gives you your battery health as a percentage.
For example, if your battery’s design capacity is 50,000 mWh and its full charge capacity is 40,000 mWh, your battery health is 80 percent.
Further down, you’ll see Battery capacity history, which shows how your battery’s capacity has changed over time. Battery life estimates show how long a charge actually lasted compared to when the battery was new.
On a Mac: Cycle Count
Apple uses a different method. Macs track battery cycles instead of a percentage. One cycle means using 100 percent of the battery’s capacity, which can happen over several days.
Apple's own route to the number:
Hold the Option key and choose System Information from the Apple menu.
Select Power in the sidebar.
Look for the Cycle Count in the Battery Information section on the right side.
In the same panel, you’ll also see a Condition line. It will say Normal or let you know if the battery needs servicing.
What the cycle number means
Current MacBook Air and MacBook Pro models are rated for 1,000 cycles.
Apple's wording is worth quoting exactly, because people misread it:
"Your battery is designed to retain up to 80% of its original charge capacity at its maximum cycle count."
So, 1,000 cycles doesn’t mean the battery is dead. It’s just when Apple expects it to hold about 80 percent of its original capacity.
Apple also says: "The battery is considered consumed when it reaches its maximum cycle count", and "You can use battery after it has reached its maximum cycle count, but you might notice a reduction in your battery life."
A Mac with 300 cycles is still early in its life. At 900 cycles, it’s getting close to the end of its rated lifespan.
What Counts as Bad
There isn’t a single industry standard, but here’s how inspections usually look at battery health.
Above 85 percent is healthy on a laptop of any age.
80 percent is the line most manufacturers design to, and most buyers accept.
If your battery health drops below 80 percent, it can lower your laptop’s resale value. The laptop will still work, but it won’t last as long unplugged, and buyers will notice this quickly.
If it’s below 60 percent, you’ll need to keep the laptop plugged in most of the time. This has a big effect on its value.
Swelling is a separate issue. If you notice the trackpad lifting, the case coming apart, or the laptop rocking on a flat surface, stop using and charging it right away. Let anyone collecting the laptop know. This is a safety concern, not just a value issue.
Should You Replace the Battery Before Selling?
Usually, you don’t need to replace the battery before selling, and the decision is similar to any other pre-sale repair.
Compare three numbers. What the laptop is worth as it is. What it would be worth with a healthy battery. What the replacement costs.
If the extra value from a new battery is more than the cost to replace it, then it’s worth doing. Most of the time, it isn’t, because battery replacement costs stay about the same while your laptop’s value drops. The older the laptop, the less sense it makes to replace the battery.
The only exception is if the battery is swollen, since that’s a safety issue, not just about value.
Our guide on selling an old laptop goes through the rest of what moves the price, and battery health is only one part of it.
How to Slow It Down
Lithium batteries wear out over time and with use. You can’t stop this, but a few habits can slow it down.
Don’t leave your laptop plugged in at 100 percent all day. Many laptops now let you cap charging at around 80 percent to help with this. Check your settings for battery protection, optimised charging, or conservation mode.
Keep your laptop cool. Heat is tougher on batteries than regular use. Gaming for hours while charging is especially hard on the battery.
If you’re storing your laptop, leave it at about half charge and keep it somewhere cool. Storing it fully charged or flat can cause the battery to swell.
Don’t worry about keeping the battery at 100 percent. Topping it up during the day is fine and actually better for the battery than letting it run down completely.
One Thing Before You Sell
No matter what your battery health is, make sure you sign out before you reset your laptop.
If you have a Mac with Apple Silicon or a T2 chip, erasing it while you’re still signed in will trigger Activation Lock. This locks the laptop to your Apple Account, and no one else can set it up. Even a perfect battery won’t help if the laptop is locked.
The same sequence applies to phones, and our guide on selling safely sets it out in full.
FAQs
1. How do I check battery health on a Windows laptop?
Open Command Prompt, type powercfg /batteryreport and press Enter. Windows saves an HTML report and tells you where. Open it, find the Installed batteries section, and divide Full Charge Capacity by Design Capacity. That is your percentage.
2. How do I check battery health on a Mac?
Hold the Option key and choose System Information from the Apple menu, select Power in the sidebar, then read the Cycle Count in Battery Information. The same panel shows a Condition line.
3. What is a good battery health percentage?
Above 85 percent is healthy. 80 percent is the level most manufacturers design to and most buyers accept. Below 80 percent begins to affect resale, and below 60 percent the laptop really needs to stay plugged in.
4. How many cycles should a MacBook battery last?
Current MacBook Air and MacBook Pro models are rated at 1,000 cycles. Apple says the battery is designed to retain up to 80 percent of its original capacity at that point, so it is not a failure point. A Mac can keep working past it with shorter battery life.
5. What is one battery cycle?
Using 100 percent of the battery's capacity, which does not have to happen in one sitting. Using half today and half tomorrow counts as one cycle.
6. Does low battery health reduce what my laptop is worth?
Yes, below about 80 percent. It is one of the first things checked at inspection, and it is easy to verify, so there is no point hiding it.
7. Should I replace the battery before selling?
Usually not. Compare what the laptop is worth now, what it would be worth with a new battery, and what the replacement costs. Replacement prices stay roughly flat while the laptop loses value, so the case gets weaker as the laptop ages.
Sources
Microsoft Learn, powercfg command line options, for the /batteryreport syntax and Microsoft's description of what the report contains and where it is saved
Apple, "Determine battery cycle count for Mac laptops", for the menu path, the 1,000 cycle rating on current MacBook Air and MacBook Pro models, and the statement that the battery is designed to retain up to 80 percent of original charge capacity at its maximum cycle count
Rabina KhadkaPublished at: Nov 9, 2026·9 min read
