Contact

Email us at [email protected] — we read everything.

Especially useful

• Numeric corrections: if any worked example doesn't reproduce to the stated precision, tell us the page and your inputs.
• Formula requests: which textbook convention or calculation family should we add next?
• Bug reports: the page, what you entered, what you expected, and what you got.

We can't give investment, tax, or accounting advice, and we can't review your specific deal — the calculators here run textbook formulas, and decisions belong with you and your qualified advisors.