How to Calculate Unix File Permissions (chmod)
Published September 16, 2026 · 2 min read
Unix file permissions can be written as a three-digit octal number or as a nine-character symbolic string, and translating between the two in your head takes a moment of bit-math. This tool converts instantly in either direction.
Try Chmod CalculatorSteps
- 1
Open the Chmod Calculator tool
Go to the chmod calculator.
- 2
Choose a direction
Convert octal to symbolic, or symbolic to octal.
- 3
Enter the permission value
Type a value like "755" or "rwxr-xr-x".
- 4
Read the breakdown
See the equivalent form, plus owner, group and other permissions listed separately, and a ready-to-use chmod command.
Frequently asked questions
Each digit represents read (4), write (2) and execute (1) permissions, summed together, for the owner, group, and everyone else, in that order — so 755 means the owner gets all three (7), while group and others get read and execute only (5).
Yes — switch the direction setting to convert a string like "rwxr-xr-x" back into its octal equivalent.
Yes — the result includes a chmod command line you can copy directly, with the filename as a placeholder.
Because the conversion is instant, this saves the mental math every time you need to translate between chmod's two permission formats.