Calculate Linux file permissions — click checkboxes or type numbers.
Chmod Calculator is a free online tool that converts between numeric (octal) and symbolic Linux file permission formats. Use visual checkboxes to set read, write, and execute permissions for owner, group, and others, or enter a numeric value to see the symbolic equivalent. Linux file permissions control who can read, write, and execute files and directories. The three permission groups — owner, group, and others — each have three permission types: read (r/4), write (w/2), and execute (x/1). Understanding and setting correct permissions is fundamental to Linux system administration and security. Incorrect file permissions are one of the most common causes of security vulnerabilities and application errors on Linux servers. Too permissive (777) exposes files to everyone, while too restrictive blocks legitimate access. This tool helps you calculate the exact permissions you need. Everything runs entirely in your browser. There are no usage limits and no account required. Common use cases include setting web server file permissions, configuring deployment scripts, securing sensitive configuration files, setting up correct permissions for SSH keys, troubleshooting permission denied errors, and documenting server configurations.