Chmod Calculator
Convert Linux file permissions between octal (755), symbolic (rwxr-xr-x) and chmod expressions like u+x,go-w, with setuid, setgid, sticky bit and umask.
| Read | Write | Execute | Special | |
|---|---|---|---|---|
| Owner (u) | Yes | Yes | Yes | — |
| Group (g) | Yes | — | Yes | — |
| Others (o) | Yes | — | Yes | — |
| Octal | Symbolic | Typical use |
|---|---|---|
| 600 | rw------- | Private files: SSH keys, .env, credentials |
| 644 | rw-r--r-- | Normal files: web pages, configs, documents |
| 664 | rw-rw-r-- | Files shared by a group of editors |
| 700 | rwx------ | Private directories and scripts (~/.ssh) |
| 750 | rwxr-x--- | Directories or programs for owner and group only |
| 755 | rwxr-xr-x | Directories and executables everyone may run |
| 775 | rwxrwxr-x | Shared group directories |
| 777 | rwxrwxrwx | Anyone can do anything — avoid on servers |
| 1777 | rwxrwxrwt | Shared temp directories such as /tmp |
| 2775 | rwxrwsr-x | Group project directories (new files inherit the group) |
| 4755 | rwsr-xr-x | setuid programs such as passwd |
Unix permissions answer three questions for three kinds of user: may the owner, the file's group and everyone else read, write or execute it? This calculator converts between the octal form used by chmod 755, the symbolic rwxr-xr-x that ls -l prints, and chmod expressions such as u+x,go-w, including the setuid, setgid and sticky bits. It also shows the matching umask and both chmod commands ready to copy.
How to use this tool
- Type an octal mode (644, 4755), a symbolic one (rw-r--r--, -rwxr-xr-x) or an expression (u+x,g-w) — or switch to Checkboxes and tick the permissions.
- For an expression, set the starting permissions it should change.
- Tick It is a directory if the target is a folder; this changes what X does.
- Copy the numeric or symbolic chmod command, or check the who-can-do-what table.
Formula
digit = 4 × read + 2 × write + 1 × execute; special digit = 4 × setuid + 2 × setgid + 1 × sticky
The three right-hand digits are owner, group and others. An optional fourth digit in front holds the special bits. In an expression, + adds bits, - removes them and = sets them exactly; X grants execute only to directories or files that are already executable by someone. A clause without u, g, o or a behaves like a, except that bits in your umask are left alone — so chmod +w with umask 022 only gives the owner write access.
Example
Start from 664 (rw-rw-r--) and apply u+x,g-w. The owner gains execute (rwx = 7), the group loses write (r-- = 4) and others keep read (4), giving 744, shown by ls -l as -rwxr--r--. The matching umask for 744 is 033.
Frequently asked questions
What does chmod 755 mean?
Owner 7 = read + write + execute; group 5 and others 5 = read + execute. It is the usual setting for directories and programs that everyone may use but only the owner may change.
Why does ls show a capital S or T?
A capital letter means the special bit is set but the execute bit under it is not, so it usually has no effect. A lower-case s or t means both are set.
What is the difference between chmod and umask?
chmod changes an existing file. umask removes bits from the default 777 (directories) or 666 (files) when something new is created, so umask 022 gives 755 directories and 644 files.
Should I ever use 777?
Rarely. It lets every account on the machine change or replace the file. Web servers almost always work with 755 for directories and 644 for files.
Sources
Last updated:
Page address with these inputs: https://kakao.mobile/tools/chmod-calculator/
Cite or embed this tool
kakaoCalc. (2026, November 8). Chmod Calculator. https://kakao.mobile/tools/chmod-calculator/
“Chmod Calculator.” kakaoCalc, 8 Nov. 2026, kakao.mobile/tools/chmod-calculator/.
Paste this code into your page. The widget runs in your visitors' browsers, shows no ads and keeps a link back to this page. Embedding terms