Developer Utilities

Unix Permission Calculator

Convert between chmod octal modes, rwx symbols, and special permission bits.

Unix file permissions
chmod · rwx · setuid · setgid · sticky
ScopeReadWriteExecuteDigit
Owner7
Group5
Others5
Permission result
755Octal
-rwxr-xr-xSymbolic
Command
chmod 755 <path>

Unix Permission Calculation

Convert between chmod octal modes and rwx symbolic notation, including setuid, setgid, and sticky special bits.

Reading Modes

  • Read, write, and execute have values 4, 2, and 1
  • The three groups represent owner, group, and others
  • The generated command uses a placeholder path that must be reviewed before execution

Frequently Asked Questions

What do 755 and 644 actually mean?
Each digit sums rwx values (r=4, w=2, x=1): 755 = owner rwx, group and others r-x — for directories and executable scripts; 644 = owner rw-, group and others r-- — for regular files. Treat 777 as an alarm bell: world-writable is how incidents happen.
What is the leading fourth digit in 4755?
Special bits: 4=setuid (runs as the file’s owner), 2=setgid (inherits the group), 1=sticky (in a directory, only the owner can delete their own files — /tmp is 1777). setuid is common on privileged system tools and a prime audit target.
What permissions should a web server deployment use?
Rules of thumb: directories 755, static files 644, config files with secrets 600, upload directories writable by the runtime user but not executable. Principle: least privilege — the process reads what it needs, writes only where it must.