About this tool
Tick the read, write and execute boxes for owner, group and other and read off the octal mode, the symbolic string and a ready-to-paste chmod command — or type the octal or symbolic form and watch the boxes follow. Common presets cover 644 for files, 755 for directories and scripts, and 600 for private keys.
The special bits are handled properly, including the detail most calculators get wrong: setuid, setgid and sticky render as a capital S or T when the underlying execute bit is off, which is exactly the case where a mode is likely to be a mistake. Risky modes such as world-writable 777 are flagged.