Chmod Calculator
Work out Unix file permissions and the chmod number from tick-boxes, and back again.
Permissions without the guesswork
Unix file permissions come as a number like 755 or 644, encoding read, write and execute rights for the owner, the group and everyone else. Remembering which number means what is a common stumble. This lets you tick the permissions you want and gives you the chmod number, or enter a number and see exactly what it grants — so you set permissions deliberately rather than copying a number and hoping.
Toggle the permissions or enter a number, and the other updates.
The numbers you'll actually use
A few values cover most cases. 755 is typical for directories and executable files — the owner can do everything, others can read and run. 644 suits regular files — the owner can read and write, others only read. And 777, which grants everyone full control, is almost always a mistake and a security risk that people reach for to fix a permissions problem without understanding it. Knowing what a number means before you apply it is exactly what avoids that trap.
Frequently asked questions
What does a permission like 755 mean?
The owner can read, write and execute; the group and everyone else can read and execute. It is common for directories and executables.
Why is 777 risky?
It gives everyone full read, write and execute access. It is almost always more than needed and a real security risk.
Is anything uploaded?
No. The calculation happens in your browser.