numvana

Chmod / Unix File Permissions Calculator

Convert a Unix/Linux chmod octal code like 755 into its symbolic permission notation, broken down by owner, group, and other.

Octal code
755
Symbolic notation
-rwxr-xr-x
Owner
rwx (read, write, execute)
Group
r-x (read, execute)
Other
r-x (read, execute)

How it works

Unix file permissions are three bits per class — read (4), write (2), execute (1) — and a permission digit 0-7 is whichever of those are added together (e.g. 5 = 4 + 1 = read + execute, no write). A chmod code like 755 is three such digits in a row, one each for the file's owner, its group, and everyone else ('other').

This decodes each digit back into its three yes/no permissions and the equivalent symbolic notation (rwx, r-x, r--, etc. — a dash means that permission is off), the same notation shown by a directory listing like `ls -l`.

This covers the standard 3-digit permission set only — it doesn't decode the optional 4th leading digit some tools accept for the setuid, setgid, and sticky bits, which are a separate, less commonly used set of special permissions.

FAQ

What does chmod 755 actually mean?

755 gives the owner full read, write, and execute access (7 = 4+2+1), while the group and everyone else get only read and execute (5 = 4+1), not write. This is a very common setting for a script or program the owner wants to edit but wants everyone to be able to run.

Why does the calculator flag 'world-writable'?

A file where the 'other' digit includes write access (any of 2, 3, 6, or 7) can be modified by any user on the system, not just its owner or group — a setting that's often a mistake and a common security review finding, so it's called out explicitly rather than left for you to notice in the raw digits.

Related calculators