Chmod Calculator

About this tool

File permissions on Unix and Linux systems are defined for three entities (owner, group and others) and three actions (read, write and execute). This calculator translates between the two notations used by the chmod command: octal (755, 644) and symbolic (rwxr-xr-x). Toggle boxes in the matrix to see octal and symbolic update instantly; you can also type either format and the matrix stays in sync. It includes common presets and a ready-to-copy command example. Everything runs in your browser with no data sent.

Use cases

• Set correct permissions when deploying files to web servers
• Translate octal permissions to readable symbolic notation
• Learn how Unix/Linux file permissions work
• Verify permissions for scripts and shared folders

Frequently asked questions

What does chmod 755 mean?

chmod 755 gives the owner all permissions (read, write and execute = 7) and the group and others only read and execute (= 5). It is the usual permission for directories and executable scripts.

What do the letters r, w and x mean in Unix permissions?

r is read (value 4), w is write (value 2) and x is execute (value 1). Each group's octal digit is the sum of the active permissions: rwx = 4+2+1 = 7.

What is the difference between owner, group and others?

Owner is the user who owns the file, group is the users in the assigned group, and others (world) is every other user on the system. Each entity has its own three permissions.

Which permissions should I use for web files?

Common practice is 644 for files (owner reads/writes, everyone else reads) and 755 for directories and executable scripts. Avoid 777: it gives full control to every user on the system.