How to show folder size in Windows

You are wondering why is it easy to see a file size in Windows explorer, but not the folder size? The short answer is – resources. In order for the explorer to show a directory size it needs to process all files in all sub folders and calculate the space that all the files take in a directory. The calculation is resource draining and time consuming. The feature was available in Windows before XP, but was then removed as it made explorer slow to work with.