💻 Developer Tools

Chmod Calculator

Tick the permission boxes and see the chmod octal number (755), symbolic notation (rwxr-xr-x) and command update instantly. Type a number to convert it back to checkboxes. setuid / setgid / sticky are supported. Everything stays in your browser.

Examples (click to try)

When in doubt, 644 (regular files) and 755 (executables and directories) are the classics.

Enter 3 digits (755) or 4 digits with a special bit (4755).

Permissions (tick to choose)
WhoRead
r · 4		Write
w · 2		Execute
x · 1
Owner u
Group g
Others o
Symbolic ---------
Command chmod 000

How to use the chmod calculator

Toggle the permission checkboxes, or type a value like 755 into the number field, and the symbolic notation (rwxr-xr-x) and chmod command update on the spot. Grab any value with its Copy button.

  • Number and checkboxes stay in sync: typing a number ticks the boxes, and ticking the boxes changes the number.
  • What each digit means: it is the sum of read r=4, write w=2 and execute x=1. So 7=rwx, 5=r-x, 4=r--.
  • Special bits: setuid / setgid / sticky add a leading fourth digit, and in symbolic notation the execute position becomes s / t (uppercase S / T when execute is off).
  • The command is ready to run: append the target file or directory name (use chmod -R to recurse into a directory).

Handy for

  • Confirming 644 (files) / 755 (directories) in a web server's public folder
  • Fixed permissions such as an SSH private key that must be 600 or it is rejected
  • Security reviews to spot overly open modes like chmod 777
  • Quickly reading "who can do what?" from a bare number

The symbolic notation is 9 characters (owner, group, others × r/w/x). In ls -l a file-type character precedes it (- for a regular file, d for a directory, l for a symlink).

FAQ

Are the values I enter sent to a server?
No. Everything is calculated entirely in your browser. The permissions and file names you enter are never transmitted to or stored on any server, so you can use it with confidence.
What do numbers like 755 or 644 mean?
From left to right the three digits are the permissions for the owner, the group and everyone else. Each digit is the sum of read (r=4), write (w=2) and execute (x=1): 7 is 4+2+1 = rwx, 5 is 4+1 = r-x, and 4 is r--. So 755 means the owner has rwx while group and others have r-x.
What are the setuid, setgid and sticky bits?
They are a special fourth digit placed in front of the usual three. setuid (4000) makes an executable run with the owner's privileges, setgid (2000) runs with the group's privileges or makes new files in a directory inherit its group, and sticky (1000) restricts a shared directory so users can only delete their own files (/tmp is the classic example). In symbolic notation they appear on the execute position as s / t (or uppercase S / T when the execute bit is off).