chmod Calculator

Toggle read/write/execute per owner, group and others to get the octal and rwx symbolic modes live, with setuid/setgid/sticky and a ready chmod command.

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This tool runs entirely in your browser. Your data never leaves your device — it is not uploaded to any server.

How to use

1Check read, write and execute for owner, group and others.
2Optionally enable setuid, setgid or sticky and watch the four-digit mode appear.
3Type a numeric mode like 644 into the reverse field to sync the checkboxes.
4Copy the chmod command and run it in your terminal.

chmod Calculator

Setting permissions on a deploy script, debugging an nginx 403, or writing a Dockerfile COPY --chmod line — Unix file permissions are a 3×3 matrix: owner, group and others each get read (4), write (2) and execute (1), and the digits stack into the octal mode. Check boxes instead of recomputing in your head.

The three special bits are covered too: setuid (4000) runs a program as the file's owner, setgid (2000) as its group, and sticky (1000) on a directory lets only the owner delete entries — think /tmp with its 1777.

Prefer working backwards? Type a number like 644 and the checkboxes sync to it, then copy the ready-made chmod command. Symbolic and octal forms are kept in sync live, so the mapping between rwxr-xr-x and 755 is always visible.

Man pages define the bits but never show the arithmetic; this calculator makes the 4-2-1 weighting explicit and renders the resulting permission string as the kernel sees it — faster and less error-prone than mental octal, especially once setuid/setgid bits enter the mix.

Frequently asked questions

What is the difference between 644 and 664?

Only the group digit changes: 644 gives the group read-only access (rw-r--r--), while 664 also lets the group write (rw-rw-r--). Both leave others with read-only. Use 644 for personal files and 664 when a shared group edits the file.

What do s and t mean in the symbolic mode?

They replace x when a special bit is set: a lowercase s in the owner or group triad means setuid or setgid combined with execute (rws), an uppercase S means the special bit without execute (rwS), and t or T marks the sticky bit on the others triad — /tmp shows drwxrwxrwt.

What is a safe default for web files?

Directories 755 and files 644 are the usual rule: you (the owner) can write, everyone else can only read. Never grant write to others (x2 in the last digit) unless a specific process truly needs it.

Is the output safe to paste into production code?

Yes. Formatting, escaping and conversion follow the relevant specs (RFCs, W3C, JSON Schema), and nothing is sent anywhere — you can verify the output locally before committing it.

Does it work on large inputs?

Yes — everything runs locally. A multi-megabyte JSON file or a long regex session is limited only by your machine, not by a request size cap.

Is this tool free to use?

Yes, completely free — no signup, no subscription, no daily limits, and no watermarks on the output.

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