One inbox, read by the person who built the calculators. The fastest route for a wrong number is the error form; everything else goes by email.
Email Ian Welkins at ianwelkins@gmail.com. Questions about how a calculator works, suggestions for a tool the site is missing, and corrections to the written guides all belong here.
Replies usually come within a few days. There is no support desk and no ticketing system — your message goes to the person who can actually change the page.
If a calculator gave you a result you believe is wrong, please use the report-an-error page instead of email. The form captures the calculator and the exact inputs you used, which is what makes the problem reproducible — 'the hip calculator is wrong' cannot be checked, but a span, pitch and overhang can.
Every report is worked by hand against the formulas. If the site is wrong, the fix ships and the correction is acknowledged; if the result was right, you get the working that shows why. Either way you hear back.
Most 'wrong answer' reports turn out to be a span entered where a run belonged, or a nominal lumber size used where an actual one was needed. Including these details up front gets your report checked in one pass: