Chmod Calculator

Convert Unix file permissions between checkboxes, octal (like 755), and symbolic (rwxr-xr-x). Includes setuid, setgid, and sticky bits. Instant, client-side.

Runs in your browser — nothing uploaded
Permissions
WhoRead (4)Write (2)Execute (1)
owner
group
other
Result
Symbolic
rwxr-xr-x
chmod 755 filename

Read = 4, write = 2, execute = 1; add them per group. Type an octal value above to work backwards. Everything is computed in your browser.

Work out Unix file permissions without memorizing the math. Tick the boxes to get the octal number for chmod (like 755) and the symbolic form (rwxr-xr-x), or type an octal value to see what it means. Includes the special setuid, setgid, and sticky bits.

Private by design — your data never leaves your device

How to use it

No account, no upload — it all happens on your device.

1
Tick the read, write, and execute boxes for owner, group, and other.
2
Add setuid, setgid, or the sticky bit if you need them.
3
Read the octal (like 755) and symbolic (rwxr-xr-x) result.
4
Or type an octal value to set the boxes in reverse.

Reading a permission string

What ls -l is telling you.

A listing like -rwxr-xr-- breaks into four parts: the file type (- for a file, d for a directory), then three triads for owner, group, and everyone else. Each triad is read (r), write (w), and execute (x), or - where the permission is absent.

Common permissions

  • 644 (rw-r--r--) — normal files: owner can edit, everyone can read.
  • 755 (rwxr-xr-x) — directories and scripts: owner full control, others can read/run.
  • 600 (rw-------) — private files like SSH keys: only the owner can read or write.

Frequently asked

How do the numbers work?
Each permission has a value: read = 4, write = 2, execute = 1. Add them for each group (owner, group, other). Read + write + execute = 7; read + execute = 5. So 'chmod 755' means owner 7 (rwx), group 5 (r-x), other 5 (r-x).
What are setuid, setgid, and the sticky bit?
They're special permissions shown as a leading fourth octal digit. setuid (4) runs a file as its owner, setgid (2) runs it as its group (or makes new files in a directory inherit the group), and the sticky bit (1) on a directory lets only a file's owner delete it — used on /tmp.
Is 777 safe?
Rarely. 777 gives everyone read, write, and execute — usually far more than needed and a security risk. Prefer the least permission that works: 644 for files and 755 for directories and scripts is a common safe default.

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