To check the total disk space left on your Windows, select File Explorer from the taskbar or press the Win + E keys, and then select This PC on the left pane. The available space on your drive/s will appear under the section Devices and drives.
WinDirStat is a free disk usage statistics viewer and cleanup tool for Windows. It displays the information you need to understand and take action on what’s taking up so much disk space on your drives.
Disk Inventory X is a free disk usage utility for Mac OS X. It shows the sizes of files and folders in a special graphical way called “treemaps”.
GrandPerspective is a utility application for macOS that graphically shows the disk usage within a file system.
If you are a Mac or a Linux user, df -h shows your system disk usage in human readable format. NCurses Disk Usage is a disk usage analyzer with an ncurses interface.