Chmod Calculator

Calculate Unix file permissions with an interactive checkbox grid. Convert between numeric and symbolic notation.

What is chmod?

chmod (change mode) is a Unix/Linux command that sets file and directory permissions. Permissions control who can read, write, and execute files. They are represented either as a three-digit octal number (e.g., 755) or as a symbolic string (e.g., rwxr-xr-x). Each digit represents permissions for the file owner, group, and others respectively, where read=4, write=2, and execute=1.

This tool converts between octal and symbolic chmod notation, and lets you interactively set permissions using checkboxes to see the resulting command.

How to Use This chmod Calculator

Use checkboxes — Toggle read, write, and execute permissions for owner, group, and others.

Or enter a number — Type an octal number (e.g., 644) to see the corresponding symbolic permissions.

View the command — The tool shows the complete chmod command ready to use in your terminal.

Copy the result — Copy the octal code, symbolic string, or full command to your clipboard.

Common Use Cases

Web server configuration — Set correct permissions for web files (644 for files, 755 for directories) to ensure security and access.

Script permissions — Make shell scripts executable with chmod 755 or restrict access with more limited permissions.

Deployment scripts — Generate the correct chmod commands for deployment automation and CI/CD pipelines.

SSH key permissions — Set proper permissions for SSH keys (600 for private keys, 644 for public keys).

Frequently Asked Questions

What does chmod 755 mean?

Chmod 755 sets the file owner to have read, write, and execute permissions (7), while the group and others have read and execute permissions (5). This is the most common permission for executable scripts and public directories.

How do I convert chmod numeric to symbolic?

Enter the numeric value (e.g., 644) in the calculator and it will show the symbolic equivalent (e.g., rw-r--r--). Each digit represents permissions for owner, group, and others: 4=read, 2=write, 1=execute.

What is the difference between chmod 644 and 755?

Chmod 644 (rw-r--r--) is typically used for regular files — the owner can read and write, everyone else can only read. Chmod 755 (rwxr-xr-x) adds execute permission, which is needed for scripts and directories.