Chmod Calculator
Calculate Unix file permissions interactively. Convert between numeric (755) and symbolic (rwxr-xr-x) notation with a visual checkbox grid.
How to Use the Chmod Calculator
- Use the checkboxes to set read, write, and execute permissions for owner, group, and others.
- Or enter a numeric value (e.g., 755) to see the corresponding permissions.
- Click a preset button for common permission configurations.
- Copy the numeric value, symbolic notation, or full chmod command.
About Chmod Calculator
Chmod (change mode) is a Unix command used to set file and directory permissions. Permissions are divided into three categories: owner (user who owns the file), group (users in the file's group), and others (everyone else). Each category can have read (r=4), write (w=2), and execute (x=1) permissions. The numeric notation sums these values: 7 means rwx (4+2+1), 5 means r-x (4+0+1), and 4 means r-- (4+0+0). Common settings include 644 for regular files (owner reads/writes, others read) and 755 for directories and executables (owner has full access, others can read and execute). Incorrect permissions are a common security vulnerability on web servers.
Frequently Asked Questions
755 gives the owner full permissions (read, write, execute), while group and others can read and execute but not write. This is the standard permission for directories and executable files.
600 (rw-------) is commonly used for sensitive files like SSH keys, giving only the owner read and write access. For files that should be read-only, 400 (r--------) is even more restrictive.
777 gives everyone full read, write, and execute permissions. This is a major security risk as any user on the system can modify or delete the file. It should almost never be used in production.