Unix Permissions Calculator (chmod)

You know what you want: the owner can do everything, the group can read, nobody else touches the file. But chmod expects a number like 755, and one wrong digit either breaks your deploy or leaves the file open to the world. Tick read, write and execute for owner, group and others here and the octal code and symbolic notation (rwxr-xr-x) update instantly, ready to use in your terminal.

Each entity gets three bits: r is worth 4, w is worth 2 and x is worth 1, and the sum forms the octal digit (rwx = 7, rw- = 6, r-x = 5). The detail that trips people up: x means something different on directories. There it grants the right to enter the folder and reach its contents, not to run anything, which is why the convention is 644 for files and 755 for directories. The calculator covers the three classic digits; special bits like setuid and sticky are out of scope.

Use the presets for the common cases and be wary of 777: on a shared server, giving write access to others is asking for trouble. A private SSH key wants 600, and the ssh client itself refuses keys with looser permissions. Everything runs in your browser, nothing is sent anywhere: tick the boxes, check the symbolic string and copy the chmod command shown on screen.