PowerShell Script to Check CPU Usage Easily

Use Get-Counter '\Processor(_Total)\% Processor Time' in PowerShell to check current CPU usage percentage.

Examples

InputRun script on idle system

OutputCPU Usage: 3.45 %

InputRun script under load

OutputCPU Usage: 75.12 %

InputRun script on multi-core system

OutputCPU Usage: 22.89 %

How to Think About It

To check CPU usage, ask the system for the current processor time percentage using a built-in performance counter. This gives a snapshot of how busy the CPU is right now. The script fetches this value and shows it in a simple number format.

Algorithm

1

Request the CPU usage counter from the system.

2

Extract the CPU usage value from the returned data.

3

Format the value as a percentage with two decimals.

4

Display the formatted CPU usage to the user.

Code

powershell

try {
  $cpu = Get-Counter '\Processor(_Total)\% Processor Time'
  $usage = $cpu.CounterSamples.CookedValue
  Write-Output "CPU Usage: {0:N2} %" -f $usage
} catch {
  Write-Output "Failed to get CPU usage."
}

Output

CPU Usage: 12.34 %

Dry Run

Let's trace running the script on a system with 12.34% CPU usage.

1

Get CPU counter

Get-Counter returns an object with CPU usage data, e.g., 12.34

2

Extract usage value

Extracted value is 12.34 from the counter samples

3

Format and output

Formatted string 'CPU Usage: 12.34 %' is printed

Step	Action	Value
1	Get-Counter '\Processor(_Total)\% Processor Time'	12.34
2	Extract CookedValue	12.34
3	Output formatted string	CPU Usage: 12.34 %

Why This Works

Step 1: Get-Counter fetches CPU data

The Get-Counter cmdlet queries Windows performance counters, here specifically the total CPU usage.

Step 2: Extract the numeric value

The CPU usage percentage is inside CounterSamples.CookedValue, which is a number representing usage.

Step 3: Format output for readability

Using -f formats the number to two decimals and adds a percent sign for clear display.

Alternative Approaches

Using WMI

powershell

try {
  $cpuLoad = Get-WmiObject Win32_Processor | Measure-Object -Property LoadPercentage -Average | Select-Object -ExpandProperty Average
  Write-Output "CPU Usage: $cpuLoad %"
} catch {
  Write-Output "Failed to get CPU usage via WMI."
}

WMI method is simpler but may be slower and less real-time than Get-Counter.

Using PerformanceCounter .NET class

powershell

Add-Type -AssemblyName System.Diagnostics
$cpuCounter = New-Object System.Diagnostics.PerformanceCounter('Processor', '% Processor Time', '_Total')
Start-Sleep -Seconds 1
$usage = $cpuCounter.NextValue()
Write-Output "CPU Usage: {0:N2} %" -f $usage

This approach uses .NET classes directly and requires a short delay for accurate reading.

Complexity: O(1) time, O(1) space

Time Complexity

The script performs a single system query without loops, so it runs in constant time.

Space Complexity

It uses a fixed amount of memory to store the counter data and output string.

Which Approach is Fastest?

Using Get-Counter is fast and real-time, WMI is simpler but slower, and .NET class method requires a delay but offers flexibility.

Approach	Time	Space	Best For
Get-Counter	O(1)	O(1)	Real-time CPU usage with built-in cmdlet
WMI	O(1)	O(1)	Simple average CPU load, less real-time
.NET PerformanceCounter	O(1) + delay	O(1)	Custom .NET usage with more control