How to use the Chmod Calculator
- 1. Tick permissionsChoose read, write and execute for owner, group and others, or type an octal number.
- 2. Show the commandSee the rwx string as ls -l shows it, plus numeric and symbolic commands.
- 3. Run itCopy the command and run it on your server; the result updates as you change boxes.
How the numbers work
Each group of permissions is one digit: read is 4, write is 2 and execute is 1, and you add the ones you want. The default boxes give the owner read and write (4 + 2 = 6) and the group and others read only (4), so the mode is 644 and ls -l shows -rw-r--r--. That is the usual setting for web pages and config files: you can edit them and everyone else can only read.
Tick execute for everyone and add write for the group and you get 775, shown as -rwxrwxr-x. The tool also writes the symbolic form, such as chmod u=rw,g=r,o=r index.html, which some people find easier to read.
Common modes and special bits
- 644 files, 755 folders and scripts, 600 private keys and .env files, 700 a private folder such as ~/.ssh.
- setuid (4xxx) runs a program as its owner. It is rare and risky on your own files.
- setgid (2xxx) on a folder makes new files inherit its group, handy for shared project folders.
- sticky (1xxx) on a folder such as /tmp lets users delete only their own files.
When a special bit is set without execute, ls shows a capital S or T, which the calculator shows too. If others can write, the tool adds a warning: 777 is almost never the right fix for a permission error. Find other everyday commands in the Linux commands cheat sheet.
Frequently asked questions
What does chmod 755 mean?
Owner can read, write and execute (7); group and others can read and execute (5). It is the usual mode for folders and scripts.
Why does a folder need execute permission?
On a directory, execute means you can enter it and reach files inside. Read only lets you list the names.
Is the Chmod Calculator free?
Yes, the Chmod Calculator is free. The first time you see your first chmod command, you are asked for your name and WhatsApp number once. After that, this and every other Uncodemy tool opens straight away without the form.