Chmod Calculator
Toggle the rwx checkboxes and watch the octal number and symbolic notation sync instantly — or type any format and convert the other way.
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Read (4)Write (2)Execute (1)
Owner
Group
Others
Read-only — computed from the bits above.
How chmod numbers work
Each of the three digits stands for owner, group, and others. A digit is the sum of r = 4, w = 2, x = 1. So 7 = 4+2+1 (rwx), 6 = 4+2 (rw-), 5 = 4+1 (r-x), 4 = 4 (r--) and 0 = ---.
Cheat sheet
| Octal | Symbolic | Typical use |
|---|---|---|
| 644 | rw-r--r-- | Web files, configs |
| 755 | rwxr-xr-x | Directories, scripts |
| 600 | rw------- | SSH keys, secrets |
| 700 | rwx------ | Private directories |
FAQ
What do the numbers in chmod 755 mean?
Each digit is the permission for owner, group, and others, computed as read=4 + write=2 + execute=1. In 755, the owner gets 4+2+1=7 (rwx) while group and others get 4+1=5 (r-x).
What are rwx permissions?
r (read) lets you view a file or list a directory, w (write) lets you modify it, and x (execute) lets you run it as a program or enter a directory. Every file has one rwx triplet for its owner, its group, and everyone else.
When should I use 644 vs 755?
Use 644 (rw-r--r--) for regular files like web pages and configs: you can edit, everyone can read. Use 755 (rwxr-xr-x) for directories and executable scripts, which need the execute bit to be entered or run.
Is chmod 777 dangerous?
Yes. 777 (rwxrwxrwx) lets every user on the system read, modify, and execute the file. It is occasionally used to "fix" permission errors, but it opens the door to tampering — prefer the least privilege that works, usually 644 or 755.
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