File Permission (chmod) Calculator

Work out file permission (chmod) instantly with clear inputs, formula shown and shareable results.

About File Permission (chmod) Calculator

Unix permissions encode read as 4, write as 2 and execute as 1, summed per class of user. Owner, group and other each get one octal digit, so 750 means rwx for the owner, r-x for the group and nothing for everyone else. The execute bit means something different on directories: it grants the right to traverse into them rather than to run them.

Formula

Permission arithmetic

digit = 4 (read) + 2 (write) + 1 (execute) per class; mode = owner digit, group digit, other digit

Worked example

With the default values below, File Permission (chmod) Calculator returns Octal mode of 750. Change any input above and every figure here is recalculated in your browser.

Inputs used

Owner permissionsone of --- (0), r-- (4), rw- (6), rwx (7), r-x (5): rwx (7)
Group permissionsone of --- (0), r-- (4), rw- (6), rwx (7), r-x (5): r-x (5)
Other permissionsone of --- (0), r-- (4), rw- (6), rwx (7), r-x (5): --- (0)

Results

Octal mode: 750
Symbolic mode: rwxr-x---
Command: chmod 750 <path>
Security note: No access for other users

Step by step

1Values used
2Permission arithmetic
3Octal mode= 750
4Symbolic mode= rwxr-x---
5Command= chmod 750 <path>
6Security note= No access for other users

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why does a directory need the execute bit?

On a directory, execute means traverse. Without it you cannot access anything inside even if you can list the names, because listing needs read and entering needs execute.

What is wrong with 777?

It lets any local user or compromised process modify the file. It is almost never necessary; the correct fix is usually to set the right owner or group.