Finding the folder size of any folder within Finder on your Mac is simple, your Get Info and view the size. However, many times you want to view the folder size within the Finder window directly so you can compare folders. You can do this within Mountain Lion, and thanks to some updated background code this folder size value is cached so it is more responsive and doesn’t take as many disk operations to find the size.
Find The Size
To find the folder size and display it within Finder select the folder you want to view the folder sizes. Go to the menu bar and select View > Show View Options, alternatively press Command + J. You will be presented with the dialog window shown in the image below.
Check the box that says “Calculate all sizes”. This will calculate the folder sizes on your Mac and present them in Finder. If you want this apply to every folder press “Use as Defaults”. It will take a few minutes to calculate the folder sizes for you, far quicker if you have an SSD hard drive.
It is only a simple setting, however it took me a while to Finder it within Mountain Lion. If you worried about excessive disk access if you apply this to every folder don’t worry. Mountain Lion has been updated, so it calculates it once and then caches the result.
If it doesn’t appear on every folder, which has happened a couple of times, just re-apply the view settings.