UNIX & LINUX DEVTOOLS

Chmod Permissions Calculator

Easily calculate and convert Linux / Unix file permissions between octal digits (755, 644, 777) and symbolic notation (rwxr-xr-x).

Octal Notation

755

Symbolic Notation

-rwxr-xr-x

Command

chmod 755 filename

Owner (User)

File owner permissions

Read (r - 4)Write (w - 2)Execute (x - 1)

Grants: Read, Write, Execute

Group

User group permissions

Read (r - 4)Write (w - 2)Execute (x - 1)

Grants: Read, Execute

Public (Others)

All other users permissions

Read (r - 4)Write (w - 2)Execute (x - 1)

Grants: Read, Execute

Quick Octal Input

Type any 3-digit octal value (000–777) to update the matrix instantly:

Popular Chmod Presets & Direct Explanations

Guide

Full Access (rwxrwxrwx)

Everyone can read, write, execute. Insecure.

Details

Guide

Standard Executable (rwxr-xr-x)

Owner has full access, others can read & execute.

Details

Guide

Standard File (rw-r--r--)

Owner can read & write, others can only read.

Details

Guide

Private File (rw-------)

Only owner can read & write (ideal for SSH keys).

Details

Guide

Private Directory (rwx------)

Only owner has full control.

Details

Guide

Read & Write All (rw-rw-rw-)

All users can read and write without execution.

Details

Guide

Read-Only Owner (r--------)

Strict read-only for file owner.

Details

Understanding Linux Permissions

In Unix-like systems, every file and directory has access rights divided into three scopes:

Owner (u): The user account that created or owns the file.
Group (g): Users who belong to the group associated with the file.
Others / Public (o): All other users on the system.

Permission Values & Math

Permission	Symbol	Octal Value	Binary	Effect on File
Read	r	4	100	View or read file contents
Write	w	2	010	Modify, edit, or delete file
Execute	x	1	001	Run file as a program or script

Frequently Asked Questions

What does chmod mean?

chmod stands for 'change mode'. It is a command in Unix and Unix-like operating systems (such as Linux and macOS) used to change the access permissions of files and directories.

How do octal permissions work in chmod?

Chmod octal permissions are represented by a 3-digit number. The first digit represents Owner permissions, the second represents Group permissions, and the third represents Public (Others). Each digit is the sum of: 4 (Read), 2 (Write), and 1 (Execute). For example, 7 = 4 + 2 + 1 (rwx), and 5 = 4 + 1 (r-x).

Why is chmod 777 considered dangerous?

Chmod 777 grants Read, Write, and Execute permissions to everyone on the system (Owner, Group, and Others). Any malicious user or compromised process can modify, delete, or execute arbitrary code in that file or directory. Production systems should avoid 777.

What are the most common chmod permissions?

The most common permissions are: 755 for executable binaries and web directories, 644 for general files (HTML, CSS, images, configs), 600 for private credentials (like SSH private keys ~/.ssh/id_rsa), and 700 for private personal directories.