chmod Calculator

How to use it

Tick the boxes for the owner, the group and everyone else — or type a value like 755 or rwxr-xr-x straight into the fields. Every view stays in sync, and the commands at the bottom are ready to paste into your terminal.

How Linux permissions work

Every file has three sets of permissions:

Each set can read (r = 4), write (w = 2) and execute (x = 1). Add the numbers to get one digit per set: rwx = 4 + 2 + 1 = 7, r-x = 4 + 1 = 5. That’s why rwxr-xr-x is 755.

Common values

Special bits

• setuid (4000): an executable runs with its owner’s privileges. That’s how passwd can update /etc/shadow.
• setgid (2000): on an executable, it runs with the group’s privileges. On a directory, new files inherit the directory’s group — handy for shared project folders.
• sticky (1000): on a directory, only a file’s owner (or root) can delete or rename it, even if others can write to the directory. /tmp uses it.

In ls -l output, a lowercase s or t means the execute bit is also set; uppercase S or T means it isn’t.

FAQ

What does execute mean for a directory?

For directories, x means “may enter and access files inside”. Without it, you can’t cd into the directory, even if you can list its names with r.

How do I set different permissions for files and directories?

Use find to target each type separately:

find /var/www/site -type d -exec chmod 755 {} +
find /var/www/site -type f -exec chmod 644 {} +

What’s the difference between chmod 755 and chmod u=rwx,g=rx,o=rx?

Nothing — they set exactly the same permissions. The symbolic form is easier to read, and it also lets you change one bit without touching the rest, like chmod g+w file.