Chmod Calculator — Octal & Symbolic Permissions

About Unix file permissions

Every file and directory on a Unix-like system (Linux, macOS, BSD) carries permissions for three classes of user: the owner, the group, and others. Each class can be granted read, write, and execute access. The chmod command sets these permissions, and you can express them two ways.

Octal is compact: each class is a digit that sums read (4), write (2), and execute (1) — so 755 is rwxr-xr-x.
Symbolic spells out the nine slots directly, using r, w, x, and - for a missing permission.
A leading fourth octal digit carries the special bits — setuid, setgid, and the sticky bit — which is why you sometimes see 0755 or 4755.

Type a value in either notation above, or tick the boxes, and this tool shows you the octal, the symbolic string, a plain-English summary, and the exact chmod command to run.

How it works

Three steps. No sign-up, no upload, no wait.

Set the permissions

Tick Read, Write, and Execute for the owner, group, and others — or type an octal like 644.

Read the results

The octal, the symbolic string (rwxr-xr-x), and a ready-to-run chmod command update live.

Copy the command

Grab the full chmod command with one click and paste it into your terminal.

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Private by design.Everything happens right here in your browser. Your files are never uploaded — we never see them.

Frequently Asked Questions

What do the read, write, and execute permissions mean? ▼

Read (r) lets you view a file's contents or list a directory. Write (w) lets you change a file or add and remove items in a directory. Execute (x) lets you run a file as a program, or enter (cd into) a directory.

How does the octal number map to permissions? ▼

Each digit is a sum of three values: read = 4, write = 2, execute = 1. So 7 is read+write+execute (4+2+1), 5 is read+execute (4+1), and 6 is read+write (4+2). The three digits apply to owner, group, and others in that order — 755 means rwxr-xr-x.

What is the difference between 755 and 0755? ▼

They describe the same base permissions. The optional leading fourth digit holds the special bits — setuid (4), setgid (2), and the sticky bit (1). A leading 0 simply means none of those special bits are set, so 0755 and 755 behave identically.

What are setuid, setgid, and the sticky bit? ▼

Setuid runs an executable with the file owner's privileges. Setgid runs it with the group's privileges, or makes new files in a directory inherit that directory's group. The sticky bit on a shared directory means only a file's owner can delete or rename it — the classic use is /tmp.

Is anything sent to a server? ▼

No. This calculator is pure math and runs entirely in your browser — no permissions, file names, or commands ever leave your device.