ChmodCalc is a single-purpose site: convert Unix permission modes between the three forms you’ll actually meet — octal (755), the ls -l symbolic string (rwxr-xr-x), and chmod’s symbolic clauses (u+x, a-w, o=r) — plus the setuid/setgid/sticky bits most calculators ignore or get wrong.

Why this site exists

Most chmod calculators online are checkbox grids that emit an octal — fine until you need the other direction, or until the special bits show up. This one was built against the real command: the symbolic-clause parser follows GNU coreutils semantics (verified against a live shell — umask filtering for omitted who, = clearing the class’s whole bit mask, conditional X, copy-permissions like g=u), the ls -l field accepts pasted output including the file-type character, and s/S/t/T render exactly as your terminal would show them.

How it works

Everything is client-side JavaScript: the bidirectional conversions, the clause parser and the command preview all run in your tab. There is no backend and nothing is uploaded — load the page, switch off your network, and it all still works. The articles — permissions explained, common chmod mistakes, special bits — were written against man chmod and POSIX, and where GNU and BSD genuinely disagree (the sticky bit under o= and o+t, for one) the text says so instead of picking a side silently.

Who maintains it

ChmodCalc is maintained by a small independent team that builds focused utility sites. The bar we hold it to: every mode it shows should match what your shell would produce. Found a divergence — an edge clause, a platform quirk, a wrong description? Contact us — correctness reports get answered first.