Enter one complete mode
Use 000–777 or 0000–7777, or a nine-character ls-style permission string. A three-digit input receives an explicit zero special digit.
Octal in · every bit visible
Read a chmod mode before you use it.
Enter a three- or four-digit octal mode, choose permission bits, or paste a complete nine-character ls-style permission string. ChmodCalc canonicalizes all 12 bits as 0000–7777 and explains owner, group, others, and special bits locally. It does not inspect a filesystem or guarantee the result of a real command.
No filesystem access, ACL, umask, ownership, recursive action, backend, or indexed custom mode.
Three explicit layers
Convert, inspect, add context
Inspect all twelve bits
Read setuid, setgid, sticky, then owner, group, and others. ChmodCalc derives the exact s/S/t/T display from special and execute bits.
Choose file or directory
The same bits have different operational meaning: x executes a regular file but searches or traverses a directory. Context changes explanation, never the numeric conversion.
Finite permission references
Start from the mode you actually saw
- Convert octal 0755 to rwxr-xr-x or the complete display back to 0755.
- Compare common references 0600, 0640, 0644, 0700, 0750, 0755, and 0775 without treating them as universal recommendations.
- Decode 1777 and see why sticky changes the final x to t.
- Distinguish lowercase s/t from uppercase S/T by checking the paired execute bit.
Check before applying
Keep all twelve mode bits visible
Convert one permission mode locally and read its file or directory interpretation. Confirm ownership, ACLs, umask, filesystem, and command behavior in the real environment before changing anything.