What this tool does
On Unix and Linux, chmod sets who can read, write and execute a file. Permissions apply to three groups: the file's owner, its group, and everyone else (public). This calculator turns your choices into the octal number and symbolic string chmod understands.
How the numbers work
- Read = 4, Write = 2, Execute = 1. Add them per group.
- Example: read+write+execute = 7; read+execute = 5.
755means owner rwx, group r-x, public r-x — common for scripts and folders.644means owner rw-, group r--, public r-- — common for regular files.
Security tips
- Avoid
777(everyone can do anything) — it's a common security mistake. - Give the minimum permissions needed. Web files rarely need to be writable by the public.