Chmod Unix Permissions Calculator
Interactively calculate octal notation (755, 644), symbolic strings (rwxr-xr-x), and ready-to-run shell chmod commands.
Permission Checkboxes
| Entity | Read (4) | Write (2) | Execute (1) |
|---|---|---|---|
| Owner (User) | |||
| Group | |||
| Public (Others) |
Special Permissions (Advanced)
Calculated Permissions
What is the Chmod Unix Permissions Calculator?
The NexTools Chmod Unix Permissions Calculator is an interactive web-based utility for calculating, converting, and understanding POSIX file permissions in Linux, macOS, and Unix-like operating systems. In Unix systems, access to files and directories is partitioned among three distinct entities: the User (Owner), the Group, and Others (Public). Each entity can be granted Read (4), Write (2), and Execute (1) permissions.
This tool converts intuitive graphical permission checkboxes into both base-8 Octal representations (such as `755` or `644`) and symbolic character strings (such as `-rwxr-xr-x`). It also generates copy-pasteable terminal commands including recursive flags (`-R`) and advanced special bit calculations (SUID, SGID, and Sticky bits).
Key Capabilities & Features
Bidirectional Octal & Symbolic Calculations
Checkboxes immediately update both the 3-digit/4-digit numeric octal and standard 10-character symbolic representation.
Standard Production Presets
One-click presets for common security standards: 755 for web servers, 644 for public assets, 600 for SSH keys, and 700 for private data.
Special Bit Handling
Configures SetUID (4000), SetGID (2000), and Sticky Bit (1000) for shared `/tmp` folders or elevated binary execution.
Interactive Terminal Command Generator
Type your target directory or file name, toggle recursive traversal, and instantly copy the verified bash command.
How Unix File Permissions Work
The Binary Values
Permissions are calculated by adding values: Read = 4, Write = 2, Execute = 1. For example, Read + Write = 4 + 2 = 6. Read + Execute = 4 + 1 = 5.
The Three Roles
Permissions are grouped into three digits: `[User][Group][Others]`. Thus, `755` grants Owner Read/Write/Exec (7), Group Read/Exec (5), and Others Read/Exec (5).
Executing the Command
Run `chmod 755 filename` in your terminal to apply the permissions. For recursive directory trees, append `-R`: `chmod -R 755 /var/www/html`.
Frequently Asked Questions (FAQ)
What permissions should I set for WordPress or web servers?
Standard web hosting best practice recommends `755` for directories (allowing the web server to traverse folders) and `644` for files (readable by all, writable only by owner).
Why does SSH reject my private key with 'Permissions 0777 are too open'?
OpenSSH requires private identity keys (such as `id_rsa`) to be readable exclusively by the user. Run `chmod 600 ~/.ssh/id_rsa` or `chmod 400 ~/.ssh/id_rsa` to resolve the warning.
What is the Sticky Bit used for?
The Sticky Bit (octal 1000, symbolic `t`) prevents users from deleting or renaming files owned by other users within a shared public folder, such as `/tmp`.