How to use the Chmod Calculator
- Tick read, write and execute for owner, group and others.
- Or type a numeric mode such as 644.
- Copy the chmod command.
What does this tool do?
Each permission has a value: read = 4, write = 2, execute = 1. Adding them gives one digit per class of user — owner, group, others. So rwx (4+2+1) is 7 and r-x (4+1) is 5, making rwxr-xr-x equal to 755.
Why use it?
- Set safe permissions on web servers.
- Understand error messages about permissions.
- No more mental arithmetic.
Common modes
Typical permissions:
| Mode | Symbolic | Typical use |
|---|---|---|
| 644 | rw-r--r-- | Normal files |
| 755 | rwxr-xr-x | Folders and scripts |
| 600 | rw------- | Private keys, secrets |
| 700 | rwx------ | Private folders |
| 777 | rwxrwxrwx | Avoid — anyone can modify |
Privacy
Everything you type is processed in your browser. Nothing you enter is sent to our servers or stored by us. There's no account to create and nothing to install.
Frequently asked questions
What's the difference between 644 and 755?
644 (rw-r--r--) lets the owner read and write and everyone else only read — typical for regular files. 755 (rwxr-xr-x) adds execute permission, which directories and scripts need.
Why is chmod 777 a bad idea?
777 lets every user on the system read, change and run the file. On a web server that can let an attacker modify your files. Grant the smallest permissions that work instead.
Last reviewed by the M2Toolkit team.