What happens when my CPU usage reaches 100 percent?

CPU Usage at 100 Percent: What Happens and How to Fix It

Sometimes you’ll notice that your computer seems to be running slower than usual, and the culprit could be high CPU usage, which forces your computer to use its processor more than normal so it’s more likely to lag or freeze up.

This guide will show you what happens when your CPU usage reaches 100 percent and what causes this to happen. It will also give you some tips on how to keep CPU usage low and prevent these issues from happening in the future.

What happens when my CPU usage reaches 100 percent?

Computer users are familiar with CPU usage, the measure of how hard the processor inside their PC or laptop is working. Your computer’s processor (CPU) determines how fast it performs tasks, such as opening and running programs, rendering videos, and playing games.

When your CPU is working harder than usual, for example, when you have multiple applications open at once, your computer will slow down to compensate for its overworked processor. This can be frustrating if you’re in a hurry to finish a project or game.

When your computer’s processing power becomes maxed out, its performance slows to a crawl and your applications might crash. If you’re currently experiencing slowness, you can use Windows Task Manager to figure out which programs are slowing things down.

Here’s how:

First, right-click on your taskbar and select Task Manager.

Next, click on Performance under More details.

Finally, look for any processes with high CPU usage and close them. You can also try restarting your computer if you don’t see anything in Task Manager that looks suspicious.

Why it’s bad to let CPU usage stay 100%

On a computer, your CPU is often called your processor or just processor. It’s part of your computer’s central processing unit (CPU), and it tells your computer how to carry out operations that you tell it to do.

You can think of it as a tiny personal assistant who takes each and every instruction you give it very, very seriously. The more instructions you throw at it, though, the slower it works, and if you overload it with too many instructions at once, eventually your computer will crash and stop working altogether.

Your computer has an operating system (OS) like Windows or Mac OS X that manages all of its processes for you. When one process becomes overloaded with work while others are idle, your OS starts up another process to help handle some of those tasks so they don’t slow down other processes on your machine.

That way, your computer runs smoothly even when you’re running multiple programs simultaneously. If your processor gets overloaded, though, and can’t keep up with requests from other programs running on your computer, then it slows down everything else in order to focus on finishing its current task.

Over time, these small delays add up until your computer grinds to a halt and you need to restart it. The best thing to avoid your computer slowing down because of high CPU usage is to keep track of which applications use lots of resources and quit them when you’re not using them.

There are also tools available for both Windows and Mac OS X that allow you to monitor what applications are using resources on your machine, keeping tabs on which ones may be causing problems.

What causes high CPU usage?

The two most common reasons are malware infections, multiple applications opened in the background, and poorly written software applications.

  1. Malware (short for malicious software) is designed specifically to make computers run slowly by taking over their resources without permission. Viruses, worms, trojans, and spyware are all types of malware. Other types include adware and ransomware.

  2. Poorly written software may not be malicious itself but may have been coded inefficiently or use unnecessary features that can put stress on your computer’s resources. In either case, if you suspect that either kind of program is causing problems for you, we recommend talking to a qualified technician who can remove any unwanted programs and clean up any issues caused by them.

Otherwise, there are also steps you can take yourself to reduce overall resource usage and avoid CPU spikes:

Close unneeded programs: Closing unneeded background apps using Ctrl+Alt+Delete click on task manager and close unwanted programs.

Turn off unneeded hardware: USB devices such as thumb drives and external hard drives can suck up valuable system resources. Disconnecting them should help free up memory.

Disable unneeded services: Services running in the background can sometimes cause crashes. To disable them, go to Control Panel > Administrative Tools > Services. For each service, right-click it and select Properties > Stop.

You should know it’s not safe to disable some services, so you have to know what you are doing if you want to go on this path

Update drivers: Outdated drivers could lead to performance issues and crashes.

• Multiple applications opened in the background cause high CPU usage. Make sure you are not running multiple copies of an application at once (for example, if you have two browsers open). If you have a virus or malware installed on your computer, it can also affect your CPU performance.

When you have too many programs running at once, it makes your computer work much harder than it should, eventually slowing down your entire system and even making it crash.

Ways you can reduce your CPU Usage

Simply put, CPU usage reaches 100 percent when your CPU is running more tasks than it has the capacity for. Understanding why performance problems happen, it helps to have an understanding of how computers work.

In essence, computers are basically just super-powered calculators. Each time you click a button or open an app, your computer is performing one of millions of calculations (instructions) per second in order to carry out that command and show you what you requested on-screen.

The more tasks you ask your computer to do at once, and the more complex those tasks are, the more instructions your computer has to process. If there isn’t enough processing power left over for other instructions, they will be delayed until there is space available.

This is where high CPU usage problems come from: Your computer isn’t able to keep up with all its tasks at once, so something has to give. That something is usually background processes like email, antivirus software updates, etc., which may not seem like a big deal but can add up to lost productivity if they become frequent occurrences.

There are two ways to solve these kinds of problems: You can either reduce the number of instructions being performed by asking your computer to do less, or you can increase how many instructions your computer can complete by upgrading its hardware.

For example, if it takes 5 minutes for Excel to load and you want to edit a spreadsheet while waiting, close any unnecessary programs first so that Excel doesn’t have as much work to do.

On the other hand, if you find yourself frequently having to wait around for things to finish loading, you might need a faster processor or additional RAM to help speed things along.

If your computer is running slowly and you don’t know why try opening Task Manager (type task manager into the Windows search bar) and see which applications are using up most of your CPU resources.

Then, you can shut down any apps that are causing trouble. It’s also worth noting that some applications automatically restart themselves after crashes or errors, if you notice your computer slows down every few hours without warning, look through your start menu and see if anything looks suspicious.

If nothing looks out of place, consider restarting your computer to clear up some memory and see if performance improves afterward.


If your CPU hits 100% there is not much to worry about. This just means that you have a lot of tasks running on your computer. If you see high spikes, it may be time to upgrade or purchase more ram if needed. It also depends on how much storage space you have on your hard drive and what applications are running in the background.

We recommend taking some time and evaluating if you need additional upgrades because keeping them in check can keep your computer running for years to come.

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