Calculate Linux file permissions in numeric (octal) and symbolic notation
Read (4)
Write (2)
Execute (1)
Owner
Group
Other
Symbolic
rwxr-xr-x
Command
chmod 755 filename
Meaning
About This Tool
The chmod (change mode) command in Linux and Unix sets file and directory permissions, controlling who can read, write, or execute a file. Permissions are assigned to three roles: the file owner, the group, and all other users.
Each permission is represented by a number — read (4), write (2), execute (1) — which are added together for each role. For example, 755 means the owner can do everything (7 = 4+2+1), while the group and others can read and execute but not write (5 = 4+1).
This calculator lets you toggle permissions visually and instantly see the octal code, the symbolic notation (like rwxr-xr-x), and the ready-to-use chmod command.
How to Use
1. Click checkboxes to toggle read, write, and execute for each role (owner, group, other)
2. Or type an octal number (like 644) directly in the input field
3. The symbolic notation, octal value, and chmod command update instantly
4. Use preset buttons for common permission sets
5. Click "Copy" to copy the chmod command to your clipboard
Frequently Asked Questions
What does chmod 755 mean?
chmod 755 gives the owner full permissions (read, write, execute) and gives the group and others read and execute permissions. This is the most common permission for web directories and executable scripts.
What is the difference between 644 and 755?
644 (rw-r--r--) allows the owner to read and write, while everyone else can only read. 755 (rwxr-xr-x) adds execute permission for all users. Use 644 for regular files and 755 for directories and scripts that need to be executed.
What does the execute permission do for directories?
For directories, execute permission means the ability to enter the directory (cd into it) and access files inside. Without execute permission on a directory, you cannot list or access its contents even if you have read permission.
Is chmod 777 safe?
No. chmod 777 gives everyone full read, write, and execute access, which is a security risk. It should almost never be used on a production server. Use more restrictive permissions like 755 for directories or 644 for files.
How do I apply chmod recursively to all files in a directory?
Use the -R flag: chmod -R 755 /path/to/directory. Be careful — this sets the same permissions for both files and directories. A safer approach is to set directory permissions and file permissions separately using the find command.