Chmod Calculator
Fast, accurate and free online chmod calculator tool running directly in your browser.
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Other tools you may find usefulChmod Permission Calculator
Online tool for calculating and converting Unix/Linux file permissions. Enter the octal mode (e.g. 755) or symbolic mode (e.g. rwxr-xr-x), and the calculator will show a full breakdown of permissions for the owner, group and other users and will generate a ready-made chmod command.
What is
The chmod calculator allows you to quickly understand and convert file permissions in Unix and Linux systems. Permissions determine who can read (r), write (w), and execute (x) a given file or directory. They are assigned to three groups: owner, group and other users. The tool supports both popular notations - octal (three or four digits, e.g. 755 or 2755 with a special bit) and symbolic nine-character (e.g. rwxr-xr-x). It is useful for configuring servers, shell scripts, Docker containers and PHP file permissions.
How to use
Select the input format - octal or symbolic. Enter permissions in the "Permissions" field (e.g.755orrwxr-xr-x). Optionally, provide the name of the file you want to apply the command to. Click "Calculate Permissions". The result will show: octal value, symbolic notation, breakdown into owner/group/other with r/w/x bits unchecked, special bits (setuid, setgid, sticky) and the readychmodcommand to copy.
Octal vs. symbolic notation - differences
Unix/Linux supports two permission notations.The octal notationis three (or four) digits from 0 to 7, where each digit is the sum of the bits: 4 = read (r), 2 = write (w), 1 = execute (x). Example: 755 = owner rwx (4+2+1=7), group r-x (4+0+1=5), others r-x (5).The symbolic notationis the nine characters r/w/x/- divided into three groups of three, e.g.rwxr-xr-x. The four-digit octal notation (e.g. 2755) also encodes special bits: setuid, setgid and sticky bit.
Typical permissions and their use
- 644(rw-r--r--) – configuration files, HTML pages; the owner can write, the rest only reads.
- 755(rwxr-xr-x) – directories and executable scripts; owner has full access, others can read and run.
- 600(rw-------) – private files (e.g. SSH keys); access only for owner.
- 777(rwxrwxrwx) – full permissions for everyone; use with caution - safety hazard.
- 400(r--------) – read-only files for the owner (e.g. id_rsa).
Special bits: setuid, setgid, sticky
Setuid (4xxx)– executable file run with owner privileges (e.g./usr/bin/passwd).Setgid (2xxx)– on directory: new files inherit directory group; on file: run with owner group.Sticky bit (1xxx)– on a directory (e.g./tmp): only the owner of the file can delete it. In symbolic notation, setuid/setgid appears ass(orSwhen x is missing), sticky ast/T.
FAQ
What is the difference between chmod 755 and chmod 644?
chmod 755 (rwxr-xr-x) gives the owner full access (read, write, execute), and the group and others read and execute - typical of directories and scripts. chmod 644 (rw-r--r--) gives the owner read and write, and the rest only read - typical for HTML, CSS, configuration files.
What does chmod 777 mean?
777 (rwxrwxrwx) gives full permissions (read, write, execute) to the owner, group and all other users. This is a risky setting - anyone can modify and run the file. Avoid in production environments.
How to apply permissions recursively?
Add the-Rflag to the command:chmod -R 755 directory/. It will change the permissions of the directory and all files/subdirectories inside. Remember that files and directories usually have different permissions (e.g. 644 for files, 755 for directories).
What is a sticky bit and when to use it?
A sticky bit (chmod 1777 or chmod +t) on a directory makes it so that only the file's owner (or root) can delete it, even if others have write permissions to the directory. A classic example is/tmp- anyone can create files, but only the owner can delete them.
How to read file permissions in terminal?
Usels -l file. The first character is the type (-=file, d=directory, l=link), the next 9 are permissions in symbolic format (owner/group/others). You can also usestat -c "%a %n" fileto get the octal value.