Chmod Calculator
This chmod calculator turns Unix and Linux file permissions into the numbers and
This chmod calculator turns Unix and Linux file permissions into the numbers and
How to use Chmod Calculator
- Check the read, write, and execute boxes for owner, group, and others, or type an octal mode like 755.
- Toggle the setuid, setgid, or sticky bits if you need the special leading digit.
- Copy the octal mode, symbolic string, or full chmod command and run it in your terminal.
About Chmod Calculator
This chmod calculator turns Unix and Linux file permissions into the numbers and letters you actually type. Check the read, write, and execute boxes for the owner, group, and others, and it builds the octal mode (like 644 or 755), the symbolic string ls -l shows (like rw-r--r--), and a ready-to-copy chmod command in real time. You can also type an octal mode and the grid updates to match, so it works both directions.
Permissions add up per class: read is 4, write is 2, and execute is 1, so a class with read and write is 6 and a class with all three is 7. An optional fourth, leading digit covers the special bits: setuid (4), setgid (2), and the sticky bit (1). Those bits also change how the execute column is displayed in symbolic notation (s, S, t, or T), which the tool renders the same way ls -l does. The leading digit only appears when one of those bits is set.
Everything runs locally in your browser as JavaScript, with no uploads, accounts, or network calls. It calculates the mode string for you but does not connect to any server or change files on any machine, so you still run the resulting chmod command yourself in your own shell.
Frequently asked questions
- What does chmod 644 or 755 mean?
- Each digit is one class: owner, group, then others. 644 means the owner can read and write (6 = 4+2) while group and others can only read (4). 755 means the owner has read, write, and execute (7 = 4+2+1) and group and others have read and execute (5 = 4+1), which is common for directories and scripts.
- How do I read the symbolic notation like rwxr-xr-x?
- It is three groups of three characters for owner, group, and others. Within each group the positions are read (r), write (w), and execute (x), and a dash means that permission is off. The tool shows this string alongside the octal so you can match what ls -l prints.
- What are the setuid, setgid, and sticky bits?
- They are the optional fourth, leading octal digit: setuid (4) runs an executable as its owner, setgid (2) runs it as its group or makes new files in a directory inherit the group, and the sticky bit (1) on a shared directory stops users from deleting each other's files. When set, they also change the execute characters in the symbolic string to s, S, t, or T.
- Does this tool change file permissions on my computer?
- No. It only calculates the octal mode, symbolic string, and chmod command. Nothing is executed and no files are touched. You copy the command and run it yourself in a terminal, which is why it can run entirely in the browser.
- Is my input sent anywhere?
- No. All calculation happens in your browser with plain JavaScript. There are no uploads, no network requests, and no accounts, so nothing you enter leaves your device.
- Can I enter a mode I already have and see what it means?
- Yes. Type an octal mode such as 640, 755, or 1777 into the octal field and the checkboxes update to match, and a plain-English summary describes exactly what each class is allowed to do.