What does chmod 755 mean? Octal vs rwx explained
Updated 2026-06-21
chmod 755 means rwxr-xr-x: the owner can read, write and execute the file, while the group and everyone else can read and execute it but not modify it. Each digit in an octal mode like 755 describes one class of user, and each is just a sum of three permission values.
How the three digits work
A chmod number always has three digits, read left to right as owner, group, others. Each digit is the sum of:
- 4 = read (r)
- 2 = write (w)
- 1 = execute (x)
Add the values you want for each class. So 7 is 4+2+1 = read, write and execute (rwx). 5 is 4+0+1 = read and execute (r-x). 0 is no access (---). That is the entire system — once you can add 4, 2 and 1, you can read any mode.
755 worked out
- Owner = 7 → 4+2+1 → rwx
- Group = 5 → 4+0+1 → r-x
- Others = 5 → 4+0+1 → r-x
Put together, 755 is rwxr-xr-x. It is the classic mode for scripts, programs and directories you want everyone to use but only yourself to change.
Common modes you will actually see
- 644 (rw-r--r--) — owner reads and writes, everyone else reads only. The default for regular files like documents and HTML.
- 755 (rwxr-xr-x) — executables and directories that need to be entered and listed.
- 600 (rw-------) — private files only the owner can touch, like an SSH key.
- 777 (rwxrwxrwx) — everyone can do everything. Convenient but a security risk; avoid it on anything web-facing.
Pitfalls worth knowing
The execute bit means two different things. On a file it allows running the file as a program; on a directory it allows entering it (cd) and accessing files inside. That is why folders normally need execute even when you only want to read them.
Order matters too: chmod is owner, group, others — not the reverse. Mixing up the last two digits silently hands the wrong people access. And a leading fourth digit (like 4755) is a special bit — setuid, setgid or the sticky bit — which is a separate, more advanced topic.
Convert it instantly
Rather than do the arithmetic in your head, the chmod Permission Calculator converts both directions: type an octal mode like 755 and see the rwxr-xr-x symbolic string, or click the read/write/execute checkboxes and read off the number to paste into your chmod command. It runs entirely in your browser — nothing is uploaded and no signup is needed — so it is safe to use on permissions for sensitive servers and keys.
Stop guessing at permission bits — open the chmod Permission Calculator and convert any mode in a click.