Need a chmod command without memorizing octal arithmetic? Toggle the permission bits above, or type a value like 755 or rwxr-xr-x, and copy a command you can paste into a terminal. This chmod calculator is part of the Linux tools on TechOpt.io.
How this chmod calculator maps rwx to octal
Every file and directory has three permission classes: the owner, the group, and everyone else (others). Each class has three bits, matching chmod(1):
- read (
r) = 4 - write (
w) = 2 - execute (
x) = 1
Add the bits for a class to get one octal digit. Read and write is 6, read and execute is 5, and all three is 7. Line up owner, group, and others and you get modes like 644 or 755.
Common chmod modes
| Mode | Symbolic | Typical use |
|---|---|---|
644 | rw-r--r-- | Regular files the owner edits and everyone can read |
755 | rwxr-xr-x | Directories and scripts |
600 | rw------- | Private files such as SSH keys |
700 | rwx------ | Private directories only the owner may enter |
777 | rwxrwxrwx | World-writable — avoid on production systems |
Special bits
A fourth leading digit sets setuid (4), setgid (2), and the sticky bit (1). Setuid runs an executable as the file owner. Setgid on a directory makes new files inherit the group. The sticky bit on a shared directory (think /tmp) lets only a file’s owner delete it.
FAQ
What does chmod 755 mean?
755 means the owner can read, write, and execute (7), while the group and everyone else can read and execute but not write (5 and 5). It is the usual mode for directories and executable scripts.
What does chmod 644 mean?
644 means the owner can read and write (6), and the group and others can only read (4 and 4). That is the standard permission for regular files such as documents and web pages.
What does chmod 777 mean?
777 gives read, write, and execute to owner, group, and others. Almost nothing on a shared or internet-facing system should be world-writable like this. Prefer 755 for directories and 644 for files unless you have a specific reason.
What is rwxr-xr-x?
That is the symbolic form of 755. The nine characters are owner, group, and others, each with read (r), write (w), and execute (x). A dash means that bit is off.
Does this chmod calculator upload my files?
No. It runs entirely in your browser. Permission values never leave your machine.
Looking for more Linux how-tos? Browse the Linux guides or the rest of the tools.