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.
Your input never leaves your browser. Everything is calculated on your device; nothing you type is sent to a server.
Review generated files before you use them. Provided as-is — see Terms.
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.
The same bits mean different things on a folder. Read lets you list the names inside, write
lets you create, rename and delete files in it, and execute lets you enter it and open what is inside. Write
and read are useless without execute, which is why folders are usually 755 or 700 while files are 644 or 600.
Deleting a file needs write permission on its folder, not on the file itself. ls -l shows the
type in front: d for a folder, - for a file, as in drwxr-xr-x. Root
ignores these rules and may always read and change everything. The details are in the
GNU coreutils manual.
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.
What permissions should an SSH private key have?
600 (rw-------): only you may read and change it. ssh refuses a private key that others can read, with the error 'UNPROTECTED PRIVATE KEY FILE'. The ~/.ssh folder itself should be 700 and authorized_keys 600.
What permissions should a shared team folder have?
2775 (drwxrwsr-x) with the folder owned by the team's group: members may create and delete files, everyone else may only look, and the setgid bit (the s) makes new files inherit the folder's group so teammates can keep editing them. Use chgrp team folder first.
Is my input sent anywhere?
No. The calculation runs entirely in your browser; nothing you type is transmitted.