The ready-to-run command updates as you go. Tick the read, write and execute boxes for the owner, group and everyone else, and get the matching octal number, the letter form and a chmod command to copy. It is free and runs in your browser.
How to use the calculator
- Under Who, tick Read, Write and Execute for the owner, the group and others.
- Read the permission in Octal (such as 755) and Symbolic (such as rwxr-xr-x) forms.
- Or type an octal number or a symbolic string and see the boxes update.
- Press Copy to take the full chmod command.
How the numbers work
Each digit is the sum of read (4), write (2) and execute (1). The first digit is the owner, the second the group and the third everyone else, so 7 is 4+2+1 for full access, 5 is read and execute and 4 is read only. 755 means the owner can do everything and others can read and run. On a folder, execute means being allowed to open it and reach the files inside.
Common permission sets
- 644: the owner can read and write, everyone else can only read. A usual choice for web pages and documents.
- 755: the owner has full access, others can read and run. Typical for scripts and folders.
- 600: only the owner can read and write. Good for private keys and secrets.
- 700: private to the owner, with execute. Useful for personal folders.
- 777: everyone can do everything. Avoid it, since it is rarely needed and risky on a shared server.
Setuid, setgid and sticky
An optional fourth digit at the front adds special bits: 4 for setuid, so a program runs as its owner; 2 for setgid, so it runs as its group, or on a folder new files inherit the folder's group; and 1 for sticky, so in a shared folder like /tmp people can only delete their own files. In the letters form they show as s or t in place of x, and as a capital S or T when execute is off.
Changing permissions with letters
The Apply a change box understands chmod's own syntax. Pick who with u, g, o or a, then + to add, - to remove or = to set exactly, then r, w and x. u+x makes a script runnable, go-w stops others writing, and a+X adds execute only to folders and files that already have it. Separate several changes with commas.
Who uses it
Web developers setting up a site, students learning Linux, and anyone managing a small server or a hosting account. For other command line helpers, see the cron expression tool and the curl converter.
Questions
What does Permission denied mean?
The account you are using lacks the needed bit on the file or folder. Check the owner, group and the permissions with the calculator, then change them with chmod.
Why can I not open a folder with 644?
Folders need execute to be opened. Use 755 instead.
Does this change files on my computer?
No. It only builds the command. You run it yourself in a terminal.