Convert between numeric (755) and symbolic (rwxr-xr-x) file permissions — including setuid, setgid and sticky bits.
Permission matrix — tick to build the mode:
| Who | Read | Write | Execute |
|---|---|---|---|
| Owner | |||
| Group | |||
| Others | |||
| Special |
Common modes: 644 = files (owner read/write, everyone read), 755 = scripts & directories, 600 = private files, 700 = private directories.
How to use this tool
e.g. 755 — or a symbolic mode like rwxr-xr-x.
Read, write and execute for owner, group and others, plus setuid/setgid/sticky.
Octal, symbolic and plain-English descriptions update together.
chmod 755 file applies the numeric form on Linux/macOS.
Formula & worked example
4755 = rwsr-xr-x: owner read/write/execute plus setuid (runs as the file's owner). 1777 = rwxrwxrwt: everyone full access plus sticky (only owners can delete their own files in a shared directory, like /tmp).
Limitations — read this before you rely on it
This covers classic Unix permission bits only — not ACLs, SELinux contexts, or Windows permissions, which layer on top. Numeric modes are shown as 4 digits including the special-bits digit; chmod also accepts 3-digit forms (leading digit assumed 0).
Frequently asked questions
Owner can read and write (6), group and others can only read (4 each). The standard for regular files.
Owner full access (7), everyone else read + execute (5). Standard for scripts and directories.
The program runs with the file owner's privileges, not the caller's — shown as s in the owner's execute position. Powerful and dangerous: never set it on files you do not fully trust.
On a directory, only a file's owner (or root) can delete or rename it, even if others can write to the directory. Classic example: /tmp (1777).
Lowercase s means the special bit is set AND execute is on. Uppercase S means the special bit is set but execute is off — usually a mistake worth fixing.