Right-click it, and select Properties from the context menu.Open File Explorer and navigate to the folder that you want to view the size of.The tool-tip will show you the size of the folder.Wait a second or two, and a tool-tip will appear.Select the folder that you want to view the size for.To show folder size in Windows 10, try these methods 1. Start off from the root of a drive and check the size of the folders there.