Build Unix file permissions with a tactile Read/Write/Execute grid for owner, group and other — including setuid, setgid and sticky bits — and watch the octal value (755), the symbolic string (rwxr-xr-x) and the chmod command update live. Type an octal value to reverse it, or apply a common preset in one click. In your browser, free.

Everything runs in your browser — no files are read and nothing is sent to the server.

Permission calculator

Toggle the boxes to set permissions, or type an octal value below to reverse it. The octal, symbolic and chmod command update instantly.

Class Readr · 4 Writew · 2 Executex · 1
Owneru
Groupg
Othero
Octal
644
Enter 3 or 4 octal digits (0–7) to set the boxes.
Symbolic
Command

Octal digit values

Each octal digit is the sum of read (4), write (2) and execute (1) for one class of user.

Digit Binary Symbolic Meaning

Common permissions

Tap “Apply” to load any preset into the calculator above.


About chmod Calculator

The chmod Calculator builds Unix file permissions visually. Toggle Read, Write and Execute for owner, group and other in a simple grid — plus the special setuid, setgid and sticky bits — and watch three outputs update live: the octal value (755), the symbolic string (rwxr-xr-x) and the complete chmod command, with an optional recursive flag.

It also works backwards: type any octal value and the grid lights up to show exactly what it grants. That reverse direction is what makes it a debugging tool as well as a builder — paste the mode from ls -l or a deployment script and see in plain checkboxes who can do what.

A digit table explains the arithmetic — each octal digit is the sum of read (4), write (2) and execute (1) — and a preset list covers the permissions you actually reach for: 644 for files, 755 for directories and executables, 600 for secrets, 750 and 775 for shared team folders, with a plain-language note on each. Everything runs in your browser.

How to use chmod Calculator

  1. Toggle the Read, Write and Execute boxes for Owner, Group and Other in the calculator grid.
  2. Enable the special bits — setuid, setgid or sticky — if you need them.
  3. Read the live octal value, symbolic string and full chmod command; tick “Recursive” to add -R.
  4. Or work in reverse: type an octal value like 640 to load it into the grid.
  5. Apply a common preset (644, 755, 600…) with one click, then copy the value or command you need.

Frequently asked questions

The owner can read, write and execute (7 = 4+2+1); group and others can read and execute (5 = 4+1) but not write. It is the standard mode for directories and executables that everyone may use but only the owner may change.

Each digit is the sum of read (4), write (2) and execute (1) for one class of user — owner, group, then other. So read plus write is 6, read plus execute is 5, and all three together make 7.

A fourth, leading octal digit. Setuid (4000) runs an executable as the file’s owner, setgid (2000) runs it as the group or makes new files in a directory inherit its group, and the sticky bit (1000) lets only a file’s owner delete it from a shared directory.

Because it lets every user on the system read, write and execute the file. On anything web-accessible that means any compromised process can modify your code. Prefer 755 for directories and executables and 644 for ordinary files.

Yes. Type the octal value — three or four digits — into the octal field and the grid, symbolic string and command all update to show exactly which permissions it grants to owner, group and other.

Yes, completely free. All calculation, reversing and copying happens in your browser — no files are read and nothing is sent to a server.

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