chmod Permission Calculator
A tool that sets Unix file permissions with read, write, and execute checkboxes for owner, group, and others, and converts between the three-digit octal used by chmod and rwx notation. It also explains what each class can do and what execute means on a directory — all processed in your browser.
Covers read, write, and execute for owner, group, and others (three octal digits). setuid, setgid, the sticky bit (fourth digit), and ACLs are not covered.
| Read (r) | Write (w) | Execute (x) | Digit | |
|---|---|---|---|---|
| Owner | 6 | |||
| Group | 4 | |||
| Others | 4 |
Result
chmod 644 file
rw-r--r--- Owner: Read (r), Write (w)
- Group: Read (r)
- Others: Read (r)
What each permission means
| On a file | On a directory | |
|---|---|---|
| Read (r) | Read the contents. | List the names of the files inside (ls). |
| Write (w) | Change the contents (deleting or renaming the file depends on write permission on the parent directory). | Create, delete, and rename files inside (execute is also required). |
| Execute (x) | Run it as a program or script. | Enter the directory (cd) and access files inside. Without it, you can't open files even if you know their names. |
How to use
- Toggle read, write, and execute for owner, group, and others.
- Or type octal (e.g. 755) or symbolic notation (e.g. rwxr-xr-x) directly; the other forms update.
- Use the common value buttons to set 644, 755, and others quickly.
- Copy the resulting chmod command.
About this tool
Each digit of chmod 755 is the permission for owner, group, and others. Read is 4, write is 2, and execute is 1, and each digit is their sum. 755 lets the owner read, write, and execute, while group and others can read and execute.
On a directory, execute means entering it and accessing files inside, and read means listing file names. That's why directories usually get read and execute together.
setuid, setgid, the sticky bit (the fourth digit), and ACLs are not covered in this version. No real file permissions are read or changed.
To inspect permissions for a private regular file, enter 600. The symbolic result is rw-------: only the owner has read (4) and write (2) permissions. Entering the same symbolic form converts it back to 600.
The calculator produces permission notation and a command example. It does not execute chmod on your files. Decide which users need access in the target environment, and check special bits or ACL settings separately.
Frequently asked questions
When should I use 644 versus 755?
Typically, regular files use 644 (only the owner can write), and executable scripts and directories use 755.
Can I use four-digit values such as 4755?
Special bits aren't supported, so four digits not starting with 0 are rejected. A leading 0, as in 0755, is treated like three digits.
Can I paste the output of ls -l?
Yes. Ten-character notation with a leading type, such as -rw-r--r-- or drwxr-xr-x, is accepted.