Unix Permissions
Translate between chmod numeric notation (755) and symbolic notation (rwxr-xr-x), tick checkboxes for each permission, and understand setuid, setgid, and the sticky bit at a glance.
0755Symbolic:rwxr-xr-xAbout the Unix Permissions Calculator
Every file and directory on a Unix-like system (Linux, macOS, BSD) carries three sets of permissions — for its owner, its group, and everyone else — plus three special bits (setuid, setgid, sticky). This free online calculator lets you flip between the numeric form used by chmod 755 file.sh and the symbolic form shown by ls -l (rwxr-xr-x), with a live permission matrix.
How Octal Notation Works
Each permission triad is encoded as an octal digit (0–7) where r = 4, w = 2, x = 1. Add them up: rw- = 6, r-x = 5, rwx = 7. The three triads combine to make a three-digit number such as 755. A leading fourth digit encodes the special bits (4000 setuid, 2000 setgid, 1000 sticky).
Common Values
755— directories, scripts, binaries (owner can edit; others can read + execute)644— regular files (owner can edit; others read-only)600— SSH private keys, sensitive configs (owner only)700— private directories (owner only)775— group-writable directories (collaborative projects)777— fully open (almost never correct in production)
Special Bits
- setuid on an executable runs it with the owner's identity. Classic use:
passwd. - setgid on a directory causes new files to inherit the directory's group — great for shared folders.
- Sticky bit on a directory means only the file's owner can delete or rename it. Set on
/tmp.
Frequently Asked Questions
Why does ls -l sometimes show s or t?
Capital or lowercase s / t in the symbolic output indicate the special bits. Lowercase means the underlying execute bit is also set; uppercase means the special bit is set but execute is not. See chmod explained.
Can I just use chmod +x instead?
Yes — chmod +x is a convenience for "add execute for everyone who can read". Numeric chmod is more explicit, which is why scripts and Dockerfiles usually prefer it.
Is the calculator aware of my files?
No. It operates on text only. Nothing is probed, read, or sent to a server.
Related Tools and Guides
Read the deep-dive in chmod explained, or generate secure passwords with the Password Generator.
Both notations
Switch between 755 and rwxr-xr-x without doing the math by hand.
Special bits
setuid, setgid, and sticky bit toggles with inline explanations.
Fully private
Everything is calculated locally — nothing touches a server.