Chmod Calculator
Convert Linux file permissions between checkboxes, octal (755) and symbolic (rwxr-xr-x) notation — with a ready-to-copy chmod command and reference table.
About the Chmod Calculator
The Chmod Calculator converts Unix/Linux file permissions between all three notations instantly. Tick read, write and execute boxes for owner, group and others, and the octal mode (like 755) and symbolic string (rwxr-xr-x) update live — or type an octal number and watch the checkboxes set themselves.
The ready-made chmod command can be copied with one click, and a reference table explains the modes you'll actually use: 644 for regular files, 755 for directories and scripts, 600 for private keys and .env files. Click any row to load it into the calculator.
Everything runs in your browser — handy when you're SSH'd into a server and just need to double-check what 664 actually grants before running it.
How to Use the Chmod Calculator
- 1Tick the read/write/execute boxes for owner, group and others — or type an octal mode like 755.
- 2Read the symbolic notation (e.g. rwxr-xr-x) that servers show in ls -l.
- 3Copy the generated chmod command and replace 'filename' with your file.
- 4Use the common-modes table to pick a safe permission for files, folders or keys.
Frequently Asked Questions
What does chmod 755 mean?
Owner gets read+write+execute (7 = 4+2+1), while group and others get read+execute (5 = 4+1). Symbolically that's rwxr-xr-x — the standard mode for directories and executable scripts.
What is the difference between chmod 644 and 755?
644 (rw-r--r--) has no execute bit — right for regular files like HTML or images. 755 adds execute for everyone, which directories need (execute = permission to enter) and scripts need to run.
Which permission should SSH private keys have?
600 (rw-------): only the owner can read or write, nobody else gets anything. SSH refuses keys with looser permissions, so run chmod 600 ~/.ssh/id_rsa if you see an 'unprotected key file' error.
How do the numbers map to permissions?
Each digit is a sum: read = 4, write = 2, execute = 1. So 6 = read+write, 5 = read+execute, 7 = all three. The three digits apply to owner, group and others in that order.
Is chmod 777 safe?
Almost never on a server — it lets any user on the system modify or execute the file. If an app 'needs' 777 to work, fix ownership with chown instead of opening permissions to everyone.