You can write to us at hello@dobcalc.top. The same address works for everything: bugs you spotted in a calculator, results that look wrong, and feature suggestions for tools you wish existed.
We usually reply within three business days.
What to include
For bug reports, a short description of what you entered, what you expected and what you saw instead is usually enough for us to reproduce the issue. For feature ideas, tell us the question you were trying to answer — that is often more useful than a proposed feature name.