Review of PowerShell Maths

Windows PowerShell Maths

PowerShell is very good at understand whether a command in your script should be handled as text or as a number.  Incidentally, the more you study PowerShell’s different math techniques, the more reasons you will find to turn to PowerShell rather than VBScript or Excel.

Topics for PowerShell Maths

For once, I favour the English word maths (plural) because we are dealing with numerous aspects of math calculation.

  1. Simple Arithmetic Operations in PowerShell
  2. PowerShell [Math]::Static Methods
  3. Measure-Object Cmdlet
  4. Get-Date Cmdlet
  5. PowerShell’s Concatenator (+)
  6. PowerShell ‘=’ Sign and -eq Operator
  7. Counters for Loops $i++


Review of Basic PowerShell Mathematics

Get started by simply typing numbers at the PowerShell command line.  You can use the 4 well-known operators + – * (asterisk) and / (forward slash), try these calculations:

68 + 47
365 -127
38 * 15
22 / 7

Simple Arithmetic Operations in PowerShell

PowerShell handles basic maths calculations, such as add and multiply with deceptive ease. Try these simple arithmetic computations:

$1stNum = 22
$2ndNum = 7
Write-Host "Add, Subtract, Multiply and Divide"
Write-Host "———————————–"
$1stNum + $2ndNum    #Add ………. Answer 29
$1stNum $2ndNum     #Subtract … Answer 15
$1stNum * $2ndNum     #Multiply …. Answer 154
$1stNum / $2ndNum     #Divide ……. Answer 3.14285 (pi)

Putting PowerShell Maths to Work

Suppose you want to test a router connection.  We could use ping, but I have chosen Win32_PingStatus.  The point is that Microsoft has designed PowerShell so that it can deal with adding 1 to

# PowerShell Ping math script
$i =1
$IPAddress = "192.168.1."
Do { $Ip4th = $IPAddress+ $i
$PingMath = Get-WmiObject Win32_PingStatus -f "Address='$Ip4th'"
$PingMath | Format-Table Address, StatusCode -hideTableHeaders -auto; $i++
Until ($i -eq 20)

Note 1: A StatusCode of 0 means a successful ping; 11003 is the equivalent of 'Destination host unreachable'.

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Review of PowerShell [Math]::Static Methods

Thanks to PowerShell accessing .Net Framework, we can perform trickier math operations; observe the static syntax, [Math]::function().  The key point here is we are asking PowerShell to employ functions such as you would use in Excel.

$1stNum = 22
$2ndNum = 7
Write-Host "[Math]::Round, Truncate and [int]"
Write-Host "———————————–"
[Math]::Round($1stNum / $2ndNum,2)
[Math]::Truncate($1stNum / $2ndNum)
[int]($1stNum / $2ndNum)

Note 2: Strictly speaking we should use [System.Math], however, the shorter [Math] works just fine.  See more on PowerShell’s static math functions.

Putting PowerShell Maths to Work

In this scenario we are investigating why a disk labelled 1 terabyte was actually only 931 gigabytes.

# PowerShell WMI class to get disk information
$Disk = Get-WmiObject Win32_diskdrive
Foreach ($Item in $Disk){
"{0,-28} {1,-20} " -f `
$Item.Name, $Item.Size}

Result: 1000202273280 (Bytes)

Let us employ PowerShell’s [Math]::Round static method to crack the problem.  Also observe where we divide by GB (gigabyte)

$Disk = Get-WmiObject Win32_diskdrive
Foreach ($Item in $Disk){
"{0,-28} {1,-20} " -f `
$Item.Name, ([Math]::Round($Item.Size/1GB,2))}

Result: 931.51 GB (GigaBytes)

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PowerShell’s Concatenator (+)

Joining text strings in PowerShell is very easy, just call for the plus sign; you can even combine text strings with numbers.  Observe how seamlessly the simple plus (+) sign joins text, numbers and the result of calculations.

The only danger is overthink, looking for extra syntax when all you need is (+)

"Guy " + "Thomas is over " + (100-40)

A more likely scenario would be combining fields, for example concatenating values stored in variables.

$FirstName = "Guy "
$Surname = "Thomas "
$Age = 64
$FirstName + $Surname + $Age

My next example is more interesting because it uses [System.Datetime] and also the static function [Math]::Truncate.

$FirstName = "Guy "
$Surname = "Thomas "
$Age = (Get-date) – ([System.Datetime]"24 June 1949")
$FirstName + $Surname + [Math]::Truncate($Age.Days/365)

Note 3: Trace the $Age variable; once again you can append a number to a text string.

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PowerShell -eq and ‘=’ Sign

For a purely mathematical calculation PowerShell uses the -eq conditional operator. The only place beginners see the equals sign in PowerShell is when assigning variables.

The -eq operator has a whole family of relatives, such as -ne (not equal), and then also the branch of the family containing greater than and less than, (-gt and -lt).

Mission: To Find Zero Length Files
Key command: Where-Object {$_.length -eq 0}

# PowerShell script to find zero length files in Windows folder
$FileSource = "C:\Windows"
$Empty = Get-ChildItem -path $Filesource -Recurse -ErrorAction SilentlyContinue
$Empty | Where-Object {$_.Length -eq 0} | Ft FullName, Length -AutoSize

Note 4: Observe the use of ‘=’ to declare variables; but -eq for the actual comparison operator.

See much more on PowerShell’s comparison operators »

Summary:  Review of Windows PowerShell Maths

PowerShell always makes an effort to understand whether your code is text or a number.  The secret of handling more complex maths functions is to understand [System.Math]:: static functions.

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See more PowerShell examples of math operations

PowerShell Maths Index   • Windows PowerShell   • PowerShell Splatting

PowerShell Math  • Comparison Operators   • PowerShell Measure Object   • Measure Command

PowerShell Tutorials  • Syntax  • Pipeline  • PowrShell Quotes  • Free WMI Monitor

Please email me if you have a better example script. Also please report any factual mistakes, grammatical errors or broken links, I will be happy to correct the fault.