Unix Permission Calculator (chmod)

Octal Input
Interactive Matrix
Owner
Read (4)
Write (2)
Execute (1)
Group
Read (4)
Write (2)
Execute (1)
Public
Read (4)
Write (2)
Execute (1)
Linux Command
$chmod 755 file
Octal Value
Numeric representation
755
Symbolic Notation
Letter representation
rwxr-xr-x

Working with the permissions of files and directories in Linux or Unix can be difficult, particularly remembering numbers associated with the chmod command. We offer you our free Chmod Calculator that features a visual interface, allowing you to obtain accurate file permissions in seconds.

Understanding Linux File Permissions

In all Unix-based operating systems, there is always a well-defined set of permissions for any file or directory, which is classified into three different categories of users: Owner, Group, and Others. Within each of these categories, the permissions are given through three basic actions, which include Read (r), Write (w), and Execute (x).

System administrators use the chmod command to modify these rights. Instead of typing out long symbolic notations (like rwxr-xr-x), administrators prefer octal notation (like 755). Our Linux permissions calculator bridges the gap between these formats, allowing you to visually toggle checkboxes to compute the exact octal value and copy the ready-to-use terminal command without manual arithmetic.

Common Scenarios for the Chmod Calculator

From configuring web servers to securing private keys, our tool helps developers quickly determine the safest permission levels.

Configure Your Web Servers

Determine the correct permissions to use such as 755 for folders and 644 for files whenever you configure your Apache or Nginx server.

Protect Your Sensitive Data

Determine strict permission requirements for your SSH keys, configurations, or database passwords using the most restrictive permissions (i.e., chmod 600/400).

Creating Deployment Scripts

Instantly convert any visual permission scheme into the respective octal command while writing a bash script, dockerfile, or even a CI pipeline.

Performing System Admin

Preview the effects of changing permissions beforehand. See exactly who will have what permission under Owner, Group, and Public sections.

Understanding File Permissions

A very useful tool to help newbies understand how octal permissions differ from symbolic ones on a typical Linux server.

Identifying Missing Permissions

Diagnose any 'Permission Denied' problem by converting the numeric permission back to its symbolic form to find the lacking permission.

Get straight-to-the-point responses to frequently asked questions on chmod octal calculations, symbolic representation, and file system security.

Frequently Asked Questions About Linux Permissions

A chmod calculator is a tool that allows you to easily generate the correct numeric (octal) or symbolic Linux file permissions by checking boxes for Read, Write, and Execute. It instantly translates your selections into a ready-to-use chmod command.
The chmod 777 permissions allow Read, Write, and Execute rights for everybody (Owner, Group, and Others). This permission level is usually not recommended for deployment purposes, as it enables everybody to change or run the file. This permission must be used solely for testing purposes.
Chmod 755 provides all permissions to the owner while other users have only read and execute permissions, making this mode popular for folders and executable shell scripts. Chmod 644 grants read and write permissions to the owner while providing other users with read permissions only, thus becoming a recommended standard for regular files such as HTML files.
The octal representation is obtained by summing up the numerical values of the different rights: read right = 4, write right = 2, execute right = 1. Thus, for read and write = 4 + 2 = 6. This is done separately for owner, group, and world to obtain an octal value of 3 digits such as 644.
Octal notation uses a 3-digit number (like 755) to represent permissions, which is highly efficient for the chmod command. Symbolic notation uses letters and dashes (like rwxr-xr-x) to visually represent the exact same access rights when you list files using the 'ls -l' command.
If you receive a 'Permission Denied' error even as a root user, the file might have the immutable attribute set, or it might be mounted on a read-only filesystem. The standard chmod command cannot override filesystem-level locks or extended attributes.
For common web servers such as Nginx and Apache, the permissions should be set as follows: 755 for folders, which allows the web server to access the folder and its files, and 644 for files in the folders.
Yes, macOS is a Unix-based operating system. The file permission concepts, including the chmod command, octal numbers, and symbolic notation, work identically on macOS terminal as they do on Linux systems.

Similar Tools

Base64 Encode & Decode
Cron Expression Generator
UUID Generator & Decoder

Disclaimer

The Unix Permission Calculator we provide runs completely in your browser. No configuration input or permissions are stored or transmitted by us to maintain total data privacy and security.