Chmod Calculator

About Chmod Calculator

A chmod calculator converts Linux and Unix file permissions between the number form (755) and the letter form (rwxr-xr-x), and gives you the command to run. Tick read, write, and execute for the owner, the group, and everyone else — or type a mode you already have — and it shows both notations, a plain-English summary, and the ready-to-copy chmod command. It all runs in your browser.

Frequently asked questions

What does chmod 755 mean?

755 means the owner can read, write, and execute, while the group and everyone else can read and execute but not write. It's the usual mode for scripts and folders. In letters it's rwxr-xr-x.

How are the numbers worked out?

Read is 4, write is 2, and execute is 1. Add up the ones you want for each of the three groups — owner, group, others. So read + write + execute = 7, and read + execute = 5, which gives 755.

What's the difference between 755 and 644?

The execute bit. 755 (rwxr-xr-x) can be run, so it suits scripts and directories — a folder needs execute to be opened. 644 (rw-r--r--) can't be run, which is right for normal files like images, text, and HTML.

Is chmod 777 safe?

Almost never. 777 lets any user on the system read, write, and delete the file. It's a common 'fix' for permission errors that leaves a real security hole — set the correct owner instead, and use 755 or 644.