Unix Permission Calculator guide
Translate Unix octal modes into symbolic read, write, execute, and special-bit permissions.
What this tool does
The Unix Permission Calculator accepts a three- or four-digit octal mode such as 755, 0640, or 4755. It turns each octal digit into owner, group, and other read, write, and execute flags. Interactive checkboxes also let you change those flags and immediately see the corresponding four-digit octal and nine-character symbolic form.
The leading octal digit represents special bits: set-user-ID, set-group-ID, and sticky. The symbolic result uses lowercase s or t when the related execute bit is also set, and uppercase S or T when it is not. This distinction matches common ls -l permission notation.
The calculator explains mode bits only. It does not connect to a filesystem, run chmod, inspect ownership, account groups, access control lists, mount options, security modules, or application behavior. Effective access can differ from these nine permission characters.
How to use it
- Enter a three- or four-digit octal mode.
- Select Load mode to populate all permission controls.
- Review owner, group, other, and special-bit selections.
- Toggle individual flags to model another mode.
- Copy the octal and symbolic results for documentation or a carefully reviewed command.
Do not apply unfamiliar permissions directly to a server. Granting world write access, set-user-ID, or set-group-ID can create serious security exposure. Follow the least-privilege requirements of the operating system and application.
Benefits
- Converts octal modes to symbolic notation
- Supports all three special permission bits
- Shows every bit as an editable control
- Explains uppercase and lowercase special symbols
- Produces a copyable result without changing files
- Performs all calculations locally
Permission context
A displayed mode cannot tell you whether a configuration is safe. File type, owner, group membership, parent-directory access, ACLs, containers, and the process account all matter. Use system documentation and test on a non-production path before changing important files.
Use the Number Base Converter for general integer conversion between binary, octal, decimal, hexadecimal, and other bases. The permission calculator adds Unix-specific owner, group, other, and special-bit interpretation.