Review configuration access
Inspect 640 to separate group reading from public access. Then confirm that the service account belongs to the intended group.
Unix permissions calculator
Calculate and convert Unix and Linux file permissions. Convert 755 to rwxr-xr-x, manage special bits and copy the matching chmod command.
- Clipboard
Convert an existing value
Permissions
| Read | Write | Execute | |
|---|---|---|---|
| Owner | |||
| Group | |||
| Others |
Special permissions
Results
Octal
Symbolic
chmod command
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How does this tool work?
Decode a mode such as 640 or rw-r-----, adjust its permissions and obtain the matching chmod command. The calculator separates owner, group and other users and includes setuid, setgid and sticky bits. Everything stays local and no file is changed. The output describes mode bits, rather than deciding whether a particular user can access a resource: ACLs, ownership, parent directories and system policies also affect the outcome.
Each group has three permissions: read r is worth 4, write w is 2 and execute x is 1. Their sum produces an octal digit from 0 to 7. In 640, the owner receives 4 + 2, the group receives 4 and others receive 0, giving rw-r-----. The first digit represents the owner, not a priority. A missing permission is shown as a hyphen in symbolic notation.
A fourth digit before the ordinary three represents special bits: setuid is 4, setgid is 2 and sticky is 1. Lowercase s or t means the special bit and execute permission are both set. Uppercase S or T means that execute permission is absent at that position. Octal input accepts three or four digits and an optional 0o prefix. Symbolic input accepts nine characters or a ten-character ls mode that includes the file type.
For directories, x permits traversal, r permits listing names and w permits changing directory entries subject to other permissions. Sticky restricts deletion or renaming in shared directories. Directory setgid affects the group of new entries. File setuid behavior depends on the system, file type and mount options. This calculator does not simulate those policies or recursive chmod changes.
How to use this tool
Load the mode
Enter an octal number or symbolic string and apply it. Relative expressions such as u+x are not accepted complete modes.
Adjust the groups
Set owner, group and other permissions. Enable a special bit only after checking its effect on your particular resource.
Adapt the command
Replace file in the suggested command with the intended path, correctly quoted for your shell. No actual path or owner is inspected here.
Use cases
Prepare a script
Compare 644 and 755 to see which groups gain execute permission. Also check the interpreter and permissions on parent directories.
Read a shared directory mode
Convert 1777 to identify sticky without mistaking it for a general write prohibition. This mode is not a universal recommendation.
Examples
A group-readable private file
640 gives the owner 6, the group 4 and others 0. The generated command uses a placeholder filename.
Input
640Result
rw-r-----
chmod 640 fileIdentify sticky
1777 retains rwx for each group and adds t at the final position. Its effect is particularly relevant to deletion in shared directories.
Input
1777Result
rwxrwxrwt
chmod 1777 fileTips and best practices
- Do not use chmod 777 as an automatic answer to access failures. Identify the group, path or policy actually blocking the operation.
- A command without -R does not recursively change a tree. Examine the affected files and directories before adding that option.
- A full ls line contains more than the mode: copy only permission characters, excluding owner, size and filename.
Sources and references
- chmod(2) — File mode bits and permission changes (opens in a new tab), Linux man-pages projectPage in English
Frequently asked questions
Why might 755 still block my application?
Mode bits are only part of access control. Parent directories, ACLs, process identity and system policies can still prevent the operation.
What is the difference between s and S?
Both indicate setuid or setgid. Lowercase includes execute permission at that position; uppercase means execute is not set.
Can I convert u+x or a-w?
No. Those are relative chmod operations. Symbolic input expects a complete nine-character state such as rwxr-xr-x.
Is the generated command executed?
No. It is text with file as a placeholder target. The browser neither reads nor changes your system’s permissions.
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