About the Chmod Calculator
The chmod calculator converts Unix file permissions between forms. Toggle read, write and execute for owner, group and other, plus the setuid, setgid and sticky bits, and it shows the octal value, the symbolic string like rwxr-xr-x and the ready-to-run chmod command. Editing the octal updates the checkboxes too, so it works both ways.
Use it when you need the right numeric mode for a script, are reviewing a permission string from ls -l, or want to understand what 755 or 644 actually grants. It runs entirely in the browser, so it is a fast reference with no install and nothing sent to a server.
How to use it
- Tick the read, write and execute boxes for owner, group and other.
- Optionally enable setuid, setgid or the sticky bit.
- Read the resulting octal value and symbolic rwx string.
- Copy the generated chmod command, or type an octal value to update the checkboxes.
Examples
- Owner rwx, group r-x, other r-x becomes octal 755, symbolic rwxr-xr-x, command chmod 755.
- Owner rw-, group r--, other r-- becomes octal 644, symbolic rw-r--r--.
- Enter 1777 for full permissions for everyone with the sticky bit set (drwxrwxrwt), as used on /tmp.
Frequently asked questions
What does the chmod calculator do?
It converts between permission checkboxes, the octal mode, the symbolic rwx string and the chmod command, so you can move between any of these forms.
Can I edit the octal value directly?
Yes. Typing an octal value updates the checkboxes, and toggling the checkboxes updates the octal, so it works in both directions.
What do setuid, setgid and the sticky bit do?
Setuid and setgid run a file with the owner's or group's privileges, and the sticky bit on a directory restricts deletion to file owners. They form the leading octal digit.
What is the difference between 755 and 644?
755 grants owner full access and read plus execute to group and other, typical for scripts and directories, while 644 grants owner read-write and read-only to others, typical for regular files.
Does it change any files on my system?
No. It only calculates the values and the command; it runs locally in your browser and does not touch your filesystem or send anything to a server.
How do I read a symbolic string like rwxr-xr-x?
It is three groups of three for owner, group and other, where r is read, w is write, x is execute and a dash means the permission is off.