Chmod Calculator

BetaThis tool is in beta. Some features may change or have limited functionality.
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Calculate and convert Linux/Unix file permissions between numeric (octal) and symbolic formats. Visual permission grid with common presets and SUID/SGID/Sticky bit support.
Numeric (Octal)
644
Symbolic
rw-r--r--
Command
chmod 644 filename

Permission Grid

OwnerGroupOthers
Read
Write
Execute

Manual Input

Special Permissions

Common Presets

Why Use Our Chmod Calculator?

File permissions are critical for Linux and Unix system security. Our chmod calculator lets you visually set permissions using an intuitive checkbox grid, instantly see the numeric (octal) and symbolic representations, and copy the ready-to-use chmod command. It supports special permissions like SUID, SGID, and Sticky bit, and includes common presets like 644, 755, and 777. Everything runs in your browser — no installation or server upload needed.

Frequently Asked Questions

What does chmod 644 mean?
chmod 644 sets the file owner to read+write (6), and group and others to read-only (4). In symbolic notation this is rw-r--r--. This is the standard permission for most files.
What does chmod 755 mean?
chmod 755 gives the owner read+write+execute (7), and group and others read+execute (5). Symbolically: rwxr-xr-x. This is the standard permission for directories and executable scripts.
What is the SUID bit?
The SUID (Set User ID) bit (4000) makes an executable run with the permissions of the file owner instead of the user running it. Common example: /usr/bin/passwd runs as root to modify /etc/shadow.
What is the difference between numeric and symbolic chmod?
Numeric chmod uses octal numbers (e.g., chmod 644) to set all permissions at once. Symbolic chmod uses letters (e.g., chmod u+x) to add or remove specific permissions. Both achieve the same result.
Is this chmod calculator free?
Yes, this chmod calculator is completely free with no signup required. All calculations happen in your browser — nothing is uploaded to any server.