Chmod Calculator

Convert between symbolic and numeric Unix file permissions with a visual chmod calculator.

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1. Toggle the checkboxes for read, write, and execute permissions for each user category: owner, group, and others. 2. View the numeric octal notation (e.g., 755) and symbolic notation (e.g., rwxr-xr-x) update in real time. 3. Alternatively, type a numeric permission value directly and see the checkboxes and symbolic notation update. 4. Use the preset buttons (644, 755, 600, etc.) to quickly load common file permission configurations. 5. Copy the generated chmod command to paste directly into your terminal.

About This Tool

The Chmod Calculator helps you understand and convert Unix/Linux file permissions between symbolic notation (rwxr-xr--) and numeric octal notation (754). Toggle individual read, write, and execute permissions for owner, group, and others using an intuitive visual interface, and see both representations update in real time.

File permissions are fundamental to Unix/Linux system security, controlling who can read, write, and execute files and directories. Getting permissions wrong can create security vulnerabilities or break application functionality. This tool removes the mental math of converting between the two notation systems.

The calculator also explains what each permission combination means in plain English, shows common permission presets (644 for files, 755 for directories and scripts, 600 for private keys), and generates the complete chmod command ready to copy and paste into your terminal. It covers special permissions including setuid, setgid, and the sticky bit.

Frequently Asked Questions

Each digit represents permissions for a different group: the first digit is the file owner, the second is the group, and the third is others (everyone else). Each digit is the sum of read (4), write (2), and execute (1). So 755 means owner has rwx (7), group has r-x (5), others have r-x (5).
644 (rw-r--r--) allows the owner to read and write, while group and others can only read. 755 (rwxr-xr-x) adds execute permission for all users. Use 644 for regular files and 755 for directories and executable scripts.
These are special permissions represented by a fourth leading digit. Setuid (4) runs a file as its owner. Setgid (2) runs it as its group or makes new files in a directory inherit the group. Sticky bit (1) prevents users from deleting files they do not own in a shared directory.
For directories, execute permission means the ability to access (enter) the directory and access files within it. Without execute on a directory, users cannot cd into it or access its contents, even if they have read permission.
Common web server permissions are 644 for files (owner read/write, everyone read) and 755 for directories (owner full, everyone read/execute). Sensitive files like configuration with passwords should use 600 (owner only). Never use 777 in production.

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