Our free Linux CHMOD Permissions Calculator provides a fast, accurate solution to translate file access rights between visual checkboxes, octal numeric codes (such as 755, 644, and 700), and symbolic notation (such as -rwxr-xr-x) directly inside your web browser. Engineered for system administrators, DevOps engineers, and web developers, it supports both standard 3-digit octal codes and 4-digit special mode bits including SetUID (4000), SetGID (2000), and the Sticky Bit (1000). Operating entirely client-side using local JavaScript, your configurations and terminal commands remain 100% private and are never sent to any external server.
Select a preset (like 755 for executables or 644 for web files) or check Read (4), Write (2), and Execute (1) for Owner, Group, and Public.
Optionally enable SetUID (4000), SetGID (2000), or Sticky Bit (1000) and toggle between File (-) or Directory (d) modes.
Instantly inspect the updated octal code, 10-character symbolic string, and copy the ready-to-run chmod command with one click.
Type any octal code directly or toggle visual permission checkboxes to see real-time synchronization across octal digits, symbolic mode syntax, and 10-character file strings.
Calculate advanced POSIX permissions including SetUID (4000), SetGID (2000), and Sticky Bit (1000) for shared directory security and privileged execution rules.
All permission arithmetic and command generations execute locally on your device in pure client-side JavaScript. No keys, paths, or commands are ever transmitted.
chmod 755 grants Read (4), Write (2), and Execute (1) permissions to the Owner, and Read (4) plus Execute (1) permissions to Group and Others. It is commonly used for Linux directories and executable scripts. chmod 644 grants Read and Write to the Owner, but Read-only to Group and Others, making it the default permission for standard web files (HTML, CSS, JS, images)./tmp) unless they own the file.- for regular files, d for directories). The remaining 9 characters are divided into 3 triads representing Owner, Group, and Others (e.g. rwxr-xr-x). Hyphens represent absent permissions, while s or t replace x when special bits are active.
Unix and Linux filesystem security uses a 3-digit octal permission system representing three user classes: Owner (u), Group (g), and Others (o). Each digit is formed by summing bitwise flags: Read (4), Write (2), and Execute (1).
Special permissions prepend a 4th octal digit: SetUID (4000) runs executable binaries with owner privileges, SetGID (2000) forces created files to inherit directory group ownership, and Sticky Bit (1000) restricts file deletion in shared folders (like /tmp) strictly to file owners.
The 10-character symbolic string formats file type and permission triads: -rwxr-xr-x for executable files or drwxr-xr-x for directories.