Converting permission numbers and rwx both ways
Every chmod call invites the same pause over what 755 actually was. Enter an octal code and the rwx notation and per-class permissions are spelled out; tick the checkboxes instead and the code fills itself in. A chmod command you can paste is built too, in both numeric and symbolic form.
Read is 4, write 2 and execute 1, and their sum forms one digit; three digits cover owner, group and other. 755 is rwxr-xr-x, 644 is rw-r--r--, 600 is rw------- and 777 is rwxrwxrwx. A fourth digit carries the special bits, setuid 4, setgid 2 and sticky 1, so 4755 is rwsr-xr-x, 2755 is rwxr-sr-x and 1777 is rwxrwxrwt. A special bit set without execute shows as an uppercase S or T.
This page converts between codes and notations only. It does not judge which permissions are appropriate, and it neither reads nor changes any real file. Changing the owner or group itself is the job of chown. Written as of October 2026.
Frequently asked questions
755 is rwxr-xr-x: the owner reads, writes and executes while group and other only read and execute. 644 is rw-r--r--: only the owner writes and everyone else reads. That is where the habit of 755 for directories and scripts and 644 for ordinary files comes from.
That slot carries a special bit. setuid changes the owner execute slot, setgid the group execute slot and sticky the other execute slot. The letter is lowercase s or t when execute is also granted and uppercase S or T when it is not.
The base permissions are set with =, as in u=rwx,g=rx,o=rx, and only the special bits are appended as u+s or o+t. Writing u=rws instead would switch execute on as well, which cannot express a mode such as 4644.