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Chmod Calculator

Understand and build Unix file permissions visually. Tick read / write / execute for owner, group, and others and watch the octal number (like 755) and symbolic string (rwxr-xr-x) update live — or type an octal value to see it decomposed. Common presets like 644, 755, 600, and 777 are one click away, with a note on when each is appropriate.

Developer Tools

Private by default

This tool runs entirely in your browser. Your data is never uploaded to a server.

How to use

3 clear steps.

  1. Tick the permissions each class (owner, group, others) should have.

  2. Read the resulting octal and symbolic notation.

  3. Or enter an octal value like 644 to see what it grants.

Good to know

Frequently asked questions

What does chmod 755 mean?
Owner: read, write, execute (7); group and others: read and execute (5). It's the standard permission for directories and executable scripts that everyone may run but only the owner may modify.
How do the octal digits map to permissions?
Each digit is the sum of read=4, write=2, execute=1 for one class. So 6 = read+write, 5 = read+execute, 7 = all three. The three digits cover owner, group, and others in order.
When should I use 777?
Almost never — 777 lets any user on the system modify the file, which is a security risk. If a web server needs write access, grant it via ownership or group permissions instead.