Chmod Calculator
Calculate Linux file permissions instantly with visual permission editor, preset configurations, and comprehensive command generation. Perfect for web server configuration, script permissions, and system administration with real-time validation and copy-to-clipboard functionality.
Permission Editor
Complete Guide: Chmod Calculator
Everything you need to know about using this tool effectively
The Chmod Calculator helps you compute Unix file permission values. You toggle read, write, and execute permissions for owner, group, and others, and the tool shows the resulting octal value (e.g., 755) and symbolic notation (e.g., rwxr-xr-x). It also shows common presets like 644, 755, and 777. All processing happens in the browser.
This tool maps nine permission bits (owner read/write/execute, group read/write/execute, others read/write/execute) to their octal representation. Each permission group contributes 0-7 to the octal value: read=4, write=2, execute=1.
Setting file permissions on a server
Calculate the correct chmod value for files and directories on a Linux server.
Configuring web server permissions
Determine the right permissions for web root files and directories.
Learning Unix permissions
Understand how read, write, and execute permissions map to octal values.
Troubleshooting permission errors
Decode an existing permission value to understand what access it grants.
Toggle permissions
Click the checkboxes to set read, write, and execute for owner, group, and others.
View the result
The octal value, symbolic notation, and chmod command update in real time.
Use presets
Click a preset for common permission combinations.
Copy the command
Copy the chmod command for use in a terminal.
644 (rw-r--r--) is standard for files: owner can read/write, others can read only.
755 (rwxr-xr-x) is standard for directories and executables.
Never use 777 (rwxrwxrwx) in production. It grants full access to everyone.
Directories need execute permission to be accessible.
What do the permission bits mean?
Read (r) allows viewing contents. Write (w) allows modifying. Execute (x) allows running as a program or entering a directory. Each applies to owner, group, and others.
What is the difference between octal and symbolic?
Octal uses numbers (e.g., 755). Symbolic uses letters (e.g., rwxr-xr-x). They represent the same permissions in different formats.
Is my data sent to a server?
No. All calculation happens in your browser. Nothing is transmitted.
What is the default umask?
The default umask is typically 022, which results in 755 for directories and 644 for files.
When should I use 755 vs 644?
Use 755 for directories and executable scripts. Use 644 for regular files that should not be executed.