Chmod Calculator

Comprehensive Overview

The Chmod Calculator converts between numeric (octal) and symbolic Unix file permissions. Unix-like operating systems (Linux, macOS, FreeBSD) use a permission system that controls read, write, and execute access for three classes: owner, group, and others. This tool provides an instant breakdown of permissions with a ready-to-use chmod command.

Key Features

• Numeric to Symbolic — Enter a numeric value like 755 and see the full symbolic representation (rwxr-xr-x).
• Symbolic to Numeric — Enter a symbolic string like rwxr-xr-x and get the numeric equivalent (755).
• Permission Breakdown — See exactly what each role (owner, group, others) can do: read, write, execute, or combinations.
• Ready Command — Get a copy-paste ready chmod 755 <file> command.

How to Use

1. Select the input mode: Numeric (e.g., 755) or Symbolic (e.g., rwxr-xr-x).
2. Enter the permission value.
3. Click Process to see the full breakdown.

Permission Values Reference

• Read (r = 4) — View file contents or list directory entries.
• Write (w = 2) — Modify file contents or add/remove files in a directory.
• Execute (x = 1) — Run a file as a program or enter a directory.

Common Permission Sets

• 644 (rw-r--r--) — Standard for files. Owner reads/writes, everyone else reads only.
• 755 (rwxr-xr-x) — Standard for directories and scripts. Owner has full access, others can read and execute.
• 600 (rw-------) — Private files. Only the owner can read and write. Recommended for SSH keys and credentials.
• 700 (rwx------) — Private directories. Only the owner has any access.
• 777 (rwxrwxrwx) — Full access for everyone. Avoid in production — serious security risk.
• 444 (r--r--r--) — Read-only for everyone. Useful for configuration files that should not be modified.