How to use the calculators, report a bug, or get in touch.
Every calculator follows the same pattern: fill in the fields on the left, click Calculate to see results on the right, and click Reset to clear the form back to its starting values. Below the calculator, a "How this works" section explains the formula, and a FAQ answers common questions specific to that calculator.
If a calculator gives an unexpected result, tell us the calculator name, the exact inputs you used, and what you expected instead. The fastest way is our Contact form — select "Report a calculator bug" as the subject.
Have an idea for a calculator we don't have yet? Use our Request a Calculator form.
For anything else, reach out via our Contact page.