Free Chmod Calculator - Linux File Permissions (Numeric & Symbolic)

What is a Chmod Calculator?

Our free online chmod calculator helps you instantly generate correct Linux file permissions in both numeric (octal) and symbolic format. Whether you're a developer, DevOps engineer, or system administrator, this tool makes managing file permissions fast and error-free.

Understanding Linux File Permissions

Owner (User)

The user who owns the file or directory.

Group

Users who belong to the assigned group.

Others

Everyone else on the system.

Frequently Asked Questions

What does chmod 755 mean?

Owner has full permissions (read+write+execute), while group and others can only read and execute. This is the most common setting for scripts and directories on web servers.

What is the difference between 755 and 644?

755 allows execution (ideal for scripts), while 644 does not (standard for regular files like images, HTML, CSS).

What are SUID, SGID, and Sticky Bit?

Advanced permissions: SUID runs a file as its owner, SGID runs as its group, and Sticky Bit prevents users from deleting others' files in a shared directory (commonly used on /tmp).

Is this tool accurate?

Yes. It follows the exact same permission logic used by Linux systems.

Common Permission Use Cases

Mode	Symbolic	Typical Use Case
600	rw-------	Private files & SSH keys (id_rsa)
644	rw-r--r--	Public web files (HTML, CSS, images)
700	rwx------	Private scripts or sensitive directories
755	rwxr-xr-x	Public directories and executable scripts
1777	rwxrwxrwt	Shared folders (Sticky Bit) like /tmp

How to Change Permissions Recursively

To apply permissions to all files and subdirectories at once, use the -R flag. However, be careful: setting 755 recursively will make your files executable too.

The "Quick" Way (Bulk):

chmod -R 755 /path/to/folder

The "Correct" Way (Different for Files/Folders):

Use these commands to set directories to 755 and files to 644 automatically.

find /var/www/html -type d -exec chmod 755 {} \;find /var/www/html -type f -exec chmod 644 {} \;

Pro-Tip: Symbolic vs. Numeric Mode

Numeric (Octal) Mode

Best for setting absolute permissions. You define the exact state for user, group, and others in one 3-digit string (e.g., 777).

Symbolic Mode

Best for making granular changes. Use + or - to add/remove specific rights (e.g., chmod +x script.sh) without affecting other bits.

Chmod Calculator

owner (User)

group (Group)

other (Others)

Special Permissions