PowerShell Script to Get a Directory Total Size

Try the following

function Get-DirectorySize() {  param ([string]$root = $(resolve-path .))  gci -re $root |    ?{ -not $_.PSIsContainer } |     measure-object -sum -property Length}

This actually produces a bit of a summary object which will include the Count of items. You can just grab the Sum property though and that will be the sum of the lengths

$sum = (Get-DirectorySize "Some\File\Path").Sum

EDIT Why does this work?

Let's break it down by components of the pipeline. The gci -re $root command will get all items from the starting $root directory recursively and then push them into the pipeline. So every single file and directory under the $root will pass through the second expression ?{ -not $_.PSIsContainer }. Each file / directory when passed to this expression can be accessed through the variable $_. The preceding ? indicates this is a filter expression meaning keep only values in the pipeline which meet this condition. The PSIsContainer method will return true for directories. So in effect the filter expression is only keeping files values. The final cmdlet measure-object will sum the value of the property Length on all values remaining in the pipeline. So it's essentially calling Fileinfo.Length for all files under the current directory (recursively) and summing the values.

If you are interested in including the size of hidden and system files then you should use the -force parameter with Get-ChildItem.

Here's quick way to get size of specific file extensions:

(gci d:\folder1 -r -force -include *.txt,*.csv | measure -sum -property Length).Sum