Chmod Calculator

Chmod Calculator is a tool for intuitively configuring file permissions (chmod) that are frequently used on Linux and macOS systems. In Unix file systems, each file and directory has three permission categories—owner, group, and other—each with read (r=4), write (w=2), and execute (x=1) flags. These permissions are expressed in two notations: a 3-digit octal number like '755' and a symbolic string like 'rwxr-xr-x'. Converting between these notations mentally can be error-prone, especially under pressure during server configuration or incident response.

This tool lets you modify permissions from any direction—checkboxes, numeric input, or symbolic input—with everything synchronized bidirectionally in real time. Frequently used permissions like 755 (owner full access only), 644 (owner read-write, others read-only), 777 (full access to everyone), and 600 (owner access only) are available as preset buttons for instant configuration. You can also easily construct permissions tailored to specific operational scenarios, such as 750 (owner and group can execute) or 711 (everyone can execute but only owner can read/write).

The calculator now supports special bits: setuid (4xxx), setgid (2xxx), and sticky bit (1xxx)—essential for advanced file management scenarios like setup scripts, shared directories, and SUID binaries. It displays three command formats simultaneously (numeric, symbolic, and recursive), making it trivial to copy and paste the correct command into your terminal.

Whether you are building a new server, deploying an application, or auditing existing file permissions, you can instantly verify the exact meaning of each chmod value and prevent security vulnerabilities and operational issues caused by incorrect permission configurations. All processing happens entirely in the browser, and no data is ever sent to an external server.