chmod Calculator

Calculate Unix file permissions.

Permissions
Read
Write
Execute
Owner
Group
Other
Command:chmod 755 filename

How to Use

Set file permissions by toggling read, write, and execute checkboxes for owner, group, and others. The tool displays the corresponding numeric (octal) notation (e.g., 755) and symbolic notation (e.g., rwxr-xr-x) in real time. You can also enter a numeric code to see the permission breakdown.

Common Use Cases

  • Calculating the correct octal permission code for shell scripts that need to be executable
  • Verifying file permissions when debugging "Permission denied" errors on Linux servers
  • Setting secure permissions for SSH keys (600) and authorized_keys files (644)
  • Documenting required file permissions in deployment runbooks and setup guides

Frequently Asked Questions

What does chmod 755 mean?

chmod 755 sets the owner to read+write+execute (7), group to read+execute (5), and others to read+execute (5). This is the standard permission for executable scripts and public directories.

What is the difference between numeric and symbolic notation?

Numeric notation uses three octal digits (e.g., 644). Symbolic notation uses letters r, w, x for read, write, execute (e.g., rw-r--r--). Both represent the same permissions; numeric is more concise, while symbolic is more readable.

What permissions should I set for SSH private keys?

SSH private keys must be set to 600 (owner read+write only) or 400 (owner read only). SSH will refuse to use a private key with permissions that are too open, as it could be read by other users.