Chmod Calculator

Tick read, write and execute for the owner, the group and others to get the octal mode (755), the symbolic mode (rwxr-xr-x) and the chmod command. Use it to set file permissions on a server or to read ls -l output.

How to use

1. Tick boxes under "Tick the permissions", or type a value under "Type an octal mode" or "Type a symbolic mode". All three stay in step.
2. Enter a change such as u+x or go-w under "Apply a symbolic change" and press "Apply".
3. Enter the "File or folder name", switch on -R if needed, and copy the "Command".
4. Paste lines into "Read an ls -l line" to see the mode, owner and name of each line.

How it works

• Each octal digit is read 4 + write 2 + execute 1, in the order owner, group, others. In a 4-digit mode the first digit is setuid 4 + setgid 2 + sticky bit 1.
• Enter a "umask value" to see the mode of new files (666 minus what the umask blocks) and new folders (777 minus what the umask blocks).
• On a folder, x means entering it (cd), so a folder without x cannot be entered even with r. The table at the bottom of the page explains this and the common values.

Questions and answers

What is the difference between chmod 755 and 644?

755 (rwxr-xr-x) lets the owner do everything and others read and run; it is common for folders and scripts. 644 (rw-r--r--) lets only the owner write and others read; it is common for files.

Is it safe to use chmod 777?

It lets anyone read, write and run the file, which is rarely needed and risky. If 755 or 644 does not work, first check the owner and group (chown).

How do I set folders to 755 and files to 644 at once?

-R gives files and folders the same mode, so use the two find commands shown at the bottom of the page.

What permissions does umask 022 give?

022 blocks write for the group and others, so new files get 644 and new folders get 755. A umask switches bits off rather than subtracting numbers: with 033, new files still get 644.