hello@numberrule.com
Write to us
Found a wrong number?
Say which page, which figure, and what you make it instead. Every calculation on this site comes from a shared engine, so a genuine error usually affects more than the page you spotted it on — which makes a report worth a good deal more than the one fix.
Corrections get looked at first and are the only messages we promise to answer.
Want a calculator that is not here?
Tell us the question you were trying to answer, in your own words. That is more useful than a tool name, because it shows what the answer has to account for.
Two kinds we will turn down, so you know before writing: anything whose answer changes on its own — tax bands, exchange rates, inflation — and anything where a wrong answer costs someone badly, such as medication dosage or child support. The reasoning is on the about page.
Anything else
Questions about how a formula works, notes on a guide, or a link that has rotted — all welcome at the same address.
We cannot help with the actual job, though. We do not know how much your builder should charge, whether to take the mortgage, or what your results mean. Those need somebody who can see the whole picture, and that is not a calculator.