In short: A chmod calculator converts Unix file permissions between checkboxes, octal numbers such as 755 and symbolic notation such as rwxr-xr-x.
About Chmod Calculator
Unix permissions are three groups of three bits: read, write and execute for the file’s owner, its group and everyone else. Each group is written as one octal digit (read = 4, write = 2, execute = 1), which is how 755 comes to mean “owner can do everything, others can read and execute”.
This calculator converts in every direction: tick boxes, type an octal value (three or four digits) or type a symbolic string like rw-r--r--. It also handles the special setuid, setgid and sticky bits, shown as s, s and t in symbolic form.
How to use Chmod Calculator
- Tick read, write and execute for owner, group and others — or type an octal or symbolic value.
- Add special bits if needed.
- Copy the generated
chmodcommand.
Examples
644 = rw-r--r--: the owner can edit, everyone else can only read. Typical for HTML, CSS and images.
755 = rwxr-xr-x: needed for executable scripts and for directories, where execute means “can enter”.
Frequently asked questions
What does chmod 777 mean?
Everyone can read, write and execute. It is almost never a good idea on a server, because any user or process can modify the file.
What is the difference between 644 and 755?
755 adds execute permission for everyone. Files that are not programs should usually be 644; directories need execute to be opened, so they are usually 755.
What does the sticky bit do?
On a directory such as /tmp, it lets users delete only their own files even though everyone can write there. Octal 1777, shown as rwxrwxrwt.
Does this change any files?
No. It only calculates values; run the command yourself on your system.
Updated November 2026 · Free, no signup · How we build and test tools