chmod calculator
Convert file permissions between 755 and rwxr-xr-x, with a plain-English explanation.
Last updated
In short: A chmod mode is one octal digit per class: owner, group and others. Each digit adds read (4), write (2) and execute (1), so 755 means rwxr-xr-x: the owner may do everything, everyone else may read and run. Type a mode or tick the boxes to get the octal, the symbolic form and the matching chmod command.
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How does the chmod calculator work?
Every file on Linux has three sets of permissions: for its owner, its
group, and everyone else. Each set is a combination of
read (4), write (2) and execute (1). Add the numbers to get one digit
per set, which is why chmod 640 means owner read+write, group read, others nothing.
An optional fourth, leading digit holds the special bits: setuid (4) runs a program 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) stops users deleting each other's files in a shared directory.
Worked examples
A script everyone may run
Input 755 gives rwxr-xr-x
The owner can read, change and run the file. Everyone else can read and run it, but not change it. This is the usual mode for scripts in /usr/local/bin.
A private config file
Input 600 gives rw-------
Only the owner can read and write. Use this for files holding passwords or keys, such as ~/.ssh/id_ed25519 or a WireGuard config.
A shared temp directory
Input 1777 gives rwxrwxrwt
Everyone can create files, but the sticky bit (the trailing t) stops users from deleting each other's files. This is how /tmp is set up.
Frequently asked questions
What does chmod 755 mean?
7 for the owner (read 4 + write 2 + execute 1), 5 for the group (read 4 + execute 1) and 5 for others. In symbolic form: rwxr-xr-x.
What is the difference between a capital S and a lowercase s?
Lowercase s means setuid or setgid is set and the execute bit is also set. Capital S means the special bit is set but execute is not, which is usually a mistake.
Why does a directory need the execute bit?
On a directory, execute means 'may enter and access files inside'. Without it, read only lets you list names; you cannot open anything in it.
Is my input sent anywhere?
No. The calculation runs entirely in your browser; nothing you type is transmitted.