Get Folder Size from Windows Command Line

Is it possible in Windows to get a folder's size from the command line without using any 3rd party tool?

I want the same result as you would get when right clicking the folder in the windows explorer → properties.

You can just add up sizes recursively (the following is a batch file):

@echo off
set size=0
for /r %%x in (folder\*) do set /a size+=%%~zx
echo %size% Bytes

However, this has several problems because cmd is limited to 32-bit signed integer arithmetic. So it will get sizes above 2 GiB wrong¹. Furthermore it will likely count symlinks and junctions multiple times so it's at best an upper bound, not the true size (you'll have that problem with any tool, though).

An alternative is PowerShell:

Get-ChildItem -Recurse | Measure-Object -Sum Length

or shorter:

ls -r | measure -sum Length

If you want it prettier:

switch((ls -r|measure -sum Length).Sum) {
  {$_ -gt 1GB} {
    '{0:0.0} GiB' -f ($_/1GB)
    break
  }
  {$_ -gt 1MB} {
    '{0:0.0} MiB' -f ($_/1MB)
    break
  }
  {$_ -gt 1KB} {
    '{0:0.0} KiB' -f ($_/1KB)
    break
  }
  default { "$_ bytes" }
}

You can use this directly from cmd:

powershell -noprofile -command "ls -r|measure -sum Length"

¹ I do have a partially-finished bignum library in batch files somewhere which at least gets arbitrary-precision integer addition right. I should really release it, I guess :-)