Contact
Open the calculator
Free, no sign-up, runs in your browser.
Write to vasanthm996@gmail.com. That address reaches a person, not a ticketing system, and it is the right place for bug reports, corrections, privacy questions and anything legal.
What to expect
This is run by one person alongside other work, so a reply usually takes a few days. A message describing what you did, what you expected and what happened instead will be answered faster than one that does not.
Postal address
Vasanth M, Trichy, Tamil Nadu, India
Reporting a problem
If a result looks wrong, send the input that produced it, the browser you used, and what you expected instead. Because everything runs on your device, there are no server logs for anyone to check — your description is the only evidence there is.