Chmod Calculator
Calculate Unix and Linux file permissions the easy way.
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Tick the read, write, and execute boxes for owner, group, and others, and get the octal chmod value (like 755) and symbolic notation (like rwxr-xr-x) instantly. Enter an octal number to reverse it. Supports setuid, setgid, and the sticky bit.
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How to Use
Tick the permission boxes
Check read, write, and execute for owner, group, and others. The octal and symbolic values update instantly as you click.
Or enter an octal value
Type a chmod number like 755 into the octal field to set the checkboxes automatically. This works in reverse too.
Add special bits if needed
Toggle setuid, setgid, or the sticky bit for advanced permission scenarios such as shared directories.
Copy the result
Copy the octal value, symbolic notation, or the ready-to-use chmod command with one click. Use the quick reference table for common presets.
Frequently Asked Questions
What is chmod and what do the numbers mean?
chmod (change mode) sets Unix file permissions. The three-digit octal number represents permissions for owner, group, and others. Each digit is the sum of read (4), write (2), and execute (1). So 755 means owner has read+write+execute (7), while group and others have read+execute (5).
What is the difference between octal and symbolic notation?
Octal notation uses numbers like 644 or 755. Symbolic notation uses letters like rw-r--r-- or rwxr-xr-x, where r=read, w=write, x=execute, and a dash means the permission is not granted. Both describe the same permissions — this calculator shows both at once.
What are setuid, setgid, and the sticky bit?
These are special permission bits. setuid (4) makes an executable run with the owner's privileges, setgid (2) makes it run with the group's privileges (or forces new files in a directory to inherit its group), and the sticky bit (1) on a directory stops users from deleting each other's files. They add a fourth leading digit to the octal value, e.g. 1777 for a sticky /tmp.
What permissions should I use for files and folders?
Common choices are 644 (rw-r--r--) for regular files, 755 (rwxr-xr-x) for folders and scripts that everyone should be able to run, 600 (rw-------) for private files like SSH keys, and 700 (rwx------) for private folders. Avoid 777 — giving everyone full access is a security risk.