Chmod Calculator
Calculate Linux/Unix file permissions with instant octal and symbolic notation.
Owner 6
Symbol: rw-
Group 4
Symbol: r--
Others 4
Symbol: r--
Result
Octal 644
Symbolic -rw-r--r--
Chmod Command
$ chmod 644 filename
Enter Octal Directly
Type 3 octal digits (0–7) to set permissions
Common Presets
About Chmod & File Permissions
Permission Types
- r Read — view file contents / list directory
- w Write — modify file / create or delete in dir
- x Execute — run as program / enter directory
Permission Entities
- Owner (u) — the file creator
- Group (g) — users sharing the group
- Others (o) — everyone else
- All (a) — owner + group + others
Octal Values
- 4 = Read
- 2 = Write
- 1 = Execute
- Add values together: 7 = rwx (4+2+1)
Common Permission Examples
| Octal | Symbolic | Meaning |
|---|---|---|
| 755 | -rwxr-xr-x | Owner full, group & others read + execute. Common for executables. |
| 644 | -rw-r--r-- | Owner read/write, others read-only. Common for web files. |
| 600 | -rw------- | Owner read/write only. Use for private SSH keys. |
| 777 | -rwxrwxrwx | Full access for all. Not recommended for security. |
| 700 | -rwx------ | Only owner can read, write, execute. |
| 444 | -r--r--r-- | Read-only for everyone. |
How to Use chmod
- chmod 755 script.sh — make script executable
- chmod -R 755 dir/ — apply recursively to directory
- chmod u+x file — add execute for owner
- chmod go-w file — remove write from group & others
Security Best Practices
- Avoid 777 — gives write access to any user on the system
- Use 600 for SSH private keys and sensitive config files
- Web server files typically use 644 (files) and 755 (dirs)
- Use ls -la to view current file permissions