Developer Tools
Chmod Calculator
Convert Unix file permissions between octal and rwx notation.
| Class | read | write | execute |
|---|---|---|---|
| owner | |||
| group | |||
| others |
Symbolic mode
rwxr-xr-xExample command
chmod 755 filename- Owner: read, write, execute
- Group: read, execute
- Others: read, execute
This calculator covers the ordinary read/write/execute bits only. It intentionally does not model setuid, setgid, sticky bits, ACLs, ownership, or platform-specific policy.
About This Tool
Unix-like systems commonly represent basic file permissions in two compact forms: symbolic letters such as rwxr-xr-x and octal digits such as 755. This calculator connects those representations. Enter a three-digit ordinary permission mode or toggle read, write, and execute for the owner, group, and others, then copy the symbolic form or a chmod command template. It is designed for understanding and checking the standard permission bits rather than blindly recommending a permission mode.
How To Use It
- Enter three octal digits from 0 to 7. The positions represent owner, group, and others.
- Review or change the read, write, and execute checkboxes. The octal value updates from the selected bits.
- Read the nine-character symbolic result in owner-group-others order.
- Copy the example chmod command only after replacing filename with the actual path and confirming that the permissions are appropriate for that file or directory.
Examples
755
Owner receives read, write, and execute (7). Group and others receive read and execute (5), producing rwxr-xr-x.
644
Owner receives read and write (6), while group and others receive read only (4), producing rw-r--r--.
700
Owner receives read, write, and execute, while group and others receive no ordinary permissions, producing rwx------.
Useful Notes
Why each octal digit is 0 through 7
The three ordinary permission bits use numeric weights: read is 4, write is 2, and execute is 1. Add the enabled weights for each class. For example, read + execute is 4 + 1 = 5, while read + write + execute is 7.
Owner, group, and others
The first octal digit applies to the file owner, the second to the file's group class, and the third to other users. Symbolic notation presents the same classes as three consecutive rwx triplets.
File and directory permissions are interpreted differently
For a regular file, read permits reading data, write permits modification, and execute permits execution when the file is otherwise executable. For a directory, read relates to listing entries, write to modifying directory entries, and execute to traversing/searching the directory. Effective access can also depend on parent directories and other controls.
This tool deliberately covers only ordinary bits
Four-digit chmod modes can include setuid, setgid, or the sticky bit. Access control lists, ownership, umask, capabilities, mount options, and security frameworks can also affect access. This calculator accepts exactly three digits so it does not imply that those additional controls have been evaluated.
Avoid copying permissive modes without understanding them
A mode such as 777 grants all three ordinary permissions to owner, group, and others. Whether any mode is appropriate depends on the file, directory, users, service, and threat model. Use the calculator to decode or construct bits, not as a security recommendation.
FAQ
What does chmod 755 mean?
It gives the owner read, write, and execute permissions, and gives group and others read and execute permissions. The symbolic form is rwxr-xr-x.
What does chmod 644 mean?
It gives the owner read and write permissions and gives group and others read permission. The symbolic form is rw-r--r--.
Why does this calculator reject 0755?
The leading digit can represent special permission bits in four-digit notation. This tool intentionally models only the three ordinary owner/group/others digits, so enter 755 instead.
Does 777 mean a file is safe to use?
No. 777 simply enables all ordinary read, write, and execute bits for all three classes. It is not a safety recommendation, and broad permissions can be inappropriate for many files and directories.
Does the calculator change any files?
No. It only converts permission values in your browser. The displayed chmod command is text for you to review and, if appropriate, run yourself in the intended environment.
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