How To Estimate Battery Life Of Any Laptop

Before buying a new laptop the first things we check are the CPU, RAM, GPU, and Hard Drive. Most buyers don’t look at the battery capacity of the laptop. Have you ever wondered why?

This is because the specs of the GPU, CPU, RAM, and HDD can tell us what programs or games we can run and store but the battery capacity numbers like 3-cell, 4-cell, 52 Wh, 72Wh doesn’t give us any info about the battery life.

Laptop manufacturers don’t reveal the exact battery life of a laptop. They tend to give us a very rough estimate but in real life the battery doesn’t perform at that level.

That is why I have written this article to help you estimate the battery life of a new as well as a used laptop.

What Are Laptop Battery Cells?

The battery capacity of a laptop is mentioned in the form of Whr and number of cells.

You will see the battery specification of a laptop denoted as 56 Whr 3-Cell or 72 Whr 6-cell, etc. But what do these Whr and number of cells mean?

A single Cell consists of two batteries that are connected in series. So, a laptop with a 3-cell battery consists of 3 pairs of cells that are connected in series to make up the whole battery.

Similarly, a 4-cell battery consists of 4 pairs of cells, a 9-cell battery consists of 9 pairs of cells and so on.

Greater the number of laptop battery cells higher is the battery life of that laptop. So, a 54 Whr 6-cell battery has a higher capacity than a 54 Whr 4-cell battery.

What is Watt Hours(Whr or Wh), MilliWatt Hour(mWh or mWhr) and Milli-Ampere Hour(mAh or mAhr)

Watt-hours, milliwatt hours and milliampere-hours are units of power consumption. For a laptop battery, it denotes the battery capacity. The battery capacity gives you the amount of energy that can be stored and supplied in one hour.

A 54 Whr battery means that the battery can store a maximum of 54 Watts in one hour and the battery can supply a maximum power of 54 Watts in one hour.

There are two more units in which battery capacity can be denoted mWh and mAh. You can easily convert them from one unit to another by the following formulas.

How To Change Whr to mAh

1 mAh = ( 1000 * Whr ) / V where V denotes the Voltage of your Laptop Battery.

So, a 48 Whr battery with a voltage of 16 V gives us ( 1000 * 48 ) / 16 = 3000 mAh.

How To Change mAh to Whr

1 Whr = ( mAh * V ) / 1000 where V denotes Voltage of Laptop battery.

So, a 3000 mAh battery with a voltage of 16 V gives us ( 3000 * 16 ) / 1000 = 48 Whr.

How To Change mWh to Whr and Whr to mWh

1 mWh = ( 1 Whr / 1000 )

So, a 42 Whr battery is equal to ( 42 / 1000 ) = 0.042 mWh.

1 Whr = 1 mWh * 1000

A 0.054 mWh battery is equal to ( 0.054 * 1000 ) = 54 Whr.

How To Check Laptop Battery Voltage

The battery Voltage of a Laptop is not mentioned in the laptop specifications for the battery section. They only mention the number of cells and the capacity in Whr. There is no mention of voltage.

But, you can easily find the battery voltage of your laptop using two ways.

The first way is by opening the back cover of your laptop and checking the voltage written on the battery. This can be tough for some people who are not tech-savvy. But don’t worry because the second way is easier than this.

Second way to check the battery voltage is by downloading a software called BatteryInfoView.

BatteryInfoView is a software that gives you a lot of information about the laptop battery. It gives you info about Battery Voltage, Battery Health, Full Charge Capacity, Designed Capacity, Battery Wear Level, Current Capacity and a lot more.

check laptop battery voltage using batteryinfoview

As you can see from the picture the battery voltage is showing as 14.946 MilliVolts(mV).

There is three other important information that this software provides. They are Designed Capacity, Full Charge Capacity, and Battery Wear Level.

Designed Capacity is the maximum amount of power a new battery can store. It can also be defined as the Battery Capacity of a Brand New Laptop Battery.

Full Charge Capacity is the amount of Power your battery can currently store.

For a brand new laptop, the Designed Capacity is the same as Full Charge Capacity because there is no wear in the battery.

For a used laptop the Full Charge Capacity is always less than the Designed Capacity because of wear in the battery.

The longer you use your laptop the lesser will be your Full Charge Capacity.

Battery Wear Level denotes the battery capacity remaining from the original battery Design Capacity.

Battery Wear Level of a brand new laptop is 100%. As you start using your laptop the battery wear level reduces due to wear and tear.

Battery Draining Activities With Rough Consumption Values

The battery of your laptop will drain no matter what you use it for. If you just turn on your laptop and leave it as it is then also the battery will drain. But, some activities consume much more battery charge than others.

Here’s a list of some of the most battery-draining tasks with a rough estimate of how much power it consumes.

Heavy Gaming / 3D Video Rendering / AI Softwares – 65 W to Maximum Capacity

Medium to Light Gaming / 4K Video Editing – 45 W to 65 W.

Photo Editing / HD 720p or HD 1080p Video Editing – 35 W to 45 W.

Streaming Netflix in HD / Watching Videos in HD – 25 W to 35 W.

Programming / Watching Offline Videos / Running Multiple Apps – 15 W to 25 W.

Web Browsing / Typing in Word or Excel / Music – 10 W to 15 W.

Leaving Laptop Alone with High Brightness and WiFi Turned On – 5 W to 10 W.

Laptop Left Alone with WiFi Turned Off – 5 W to 8 W.

These are rough estimates and it may change depending on your laptop manufacturer.

How To Determine Battery Life When Buying A New Laptop

Battery life denotes the number of hours a laptop battery can run with a single charge.

You can determine the battery life of a laptop before buying using three ways.

(a) Reading Reviews on Websites.

(b) Watching Reviews on YouTube.

(c) Calculating Battery Life Using Formula.

The first two methods give an exact idea of the battery capacity of laptop because they have used it first hand.

If you determine battery life using the formula then you should know that it is a rough estimate. You cannot determine the exact battery life using this formula.

Battery Life = ( Battery Capacity / Battery Draining Activities )

If you have an HP Spectre x360 laptop with a battery capacity of 79 Whr and you’re using it to watch videos online that consume around 26 W then you’ll get a battery life of ( 79 Whr / 26 W ) = 3.03 hours.

This value is not even close to what the Spectre x360 delivers. Spectre x360 has a battery life of around 12 hours. So, this formula is a very rough estimate.

How To Find Battery Life Of A Used Laptop

Battery life deteriorates over time because of wear and tear. A 3 months old laptop with heavy usage will have better battery life than a 6 months old laptop with heavy usage.

The battery capacity decreases with time because it cannot store as much energy as it used to before and there is a decrease in the number of charge-discharge cycles.

You can check the current battery capacity of your laptop using two methods.

METHOD 1 – BatteryInfoView

As mentioned earlier, the BatteryInfoView gives you a lot of info about your laptop battery. The two most important values for calculating battery life are Full Charge Capacity and Battery Wear Level.

Battery Wear Level is the battery percentage remaining from the original or Designed battery capacity. A brand new laptop has 100% Battery Wear Level because it hasn’t been used so there is no wear and tear.

Designed battery capacity is the maximum amount of Power a new battery can store. The designed battery capacity is calculated for 100% Battery Wear Level.

battery wear level using batteryinfoview

My current battery wear level is 92.3% which means that my battery can charge up to 92.3% of the original designed battery capacity.

Full Charge capacity takes the battery wear level into account and denotes the amount of power it can store.

METHOD 2 – Using Command Prompt

You can check the Full Charge Capacity and Design Capacity using Command Prompt. Just follow the steps below.

Step 1 – Open Command Prompt. You may be asked to Run as Administrator. Just click OK and run Command Prompt as Admin.

Step 2 – Type in the following command powercfg /batteryreport /output “C:\battery_report.html” and press Enter.

open command prompt

Step 3 – Open your C Drive and then you’ll find a file named battery_report.html

open c drive and locate battery info file

Step 4 – Open the file and navigate to Installed Batteries section. In this section you’ll find battery capacity details like Full Charge Capacity and Design Capacity.

final battery report

You can use the Full Charge Capacity to estimate the current battery life of your laptop using the formula I shared before.

How Long Does A Laptop Battery Last?

The life of a laptop battery depends on a lot of factors like usage, the number of charge-discharge cycles left, Battery Wear Level, battery charge capacity and other factors.

A normal Lithium-Ion Laptop battery lasts for around 3-5 years depending on the factors mentioned above. It can last for fewer years if you use a laptop with less battery capacity and use it heavily.

If we talk about battery life then an average laptop battery lasts for around 7-8 hours without heavy usage. I am talking about simple web browsing without doing any heavy tasks.

If you play games and use 3D rendering software like Autodesk Maya then the laptop battery won’t last even an hour.

The battery life also depends on the battery used by your laptop manufacturer. Work laptops like Lenovo Yoga Ultrabooks have a battery life of around 12 hours whereas gaming laptops like Razer Blade 15 have a battery life of around 5-6 hours.

How To Achieve Maximum Battery Life On Your Laptop

The battery life of your laptop can be increased by following these methods.

(a) Use Your Laptop On Low Brightness. It will save the battery and is also good for your eyes.

(b) If you’re not playing games then use Battery Saving or Power Saving mode to do your daily tasks.

(c) If you’re not using the WiFi then you can turn on the Aeroplane mode to save battery.

(d) Plug in your charger before the battery level reaches below 50% to decrease the rate of charge-discharge cycles and increase your battery life.

(e) Don’t play games or run 3D rendering software when your laptop is not plugged into Charge.


Determining battery life using software and formulas are not the most effective. These are just estimates and don’t guarantee an exact value.

The best way to determine the battery life is by looking at reviews for the laptop you want to buy.

If you already have a laptop then you can easily find out the battery life by measuring the charge consumed by different tasks.

One important thing you should keep an eye on is the Battery Wear Level. You can check it using the BatteryInfoView software.

1 thought on “How To Estimate Battery Life Of Any Laptop”

  1. This refers to your article “How to Estimate Battery Life Of Any Laptop.”
    Under section How To Check Laptop Battery Voltage, paragraph 6 reads “As you can see from the picture the battery voltage is showing as 14.946 MilliVolts(mV).”
    I think “14.946” should be 14,946.


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