Contact CalcOtter
One address, read by the person who writes the calculators.
hello@calcotter.com — for everything below. There is no contact form, no ticket number, and no chatbot in front of it. Messages go to the person who builds and maintains CalcOtter, and are normally answered within two business days.
Reporting a wrong number
This is the message we most want to receive, and it gets answered first. A calculator that disagrees with a textbook is a bug, not a matter of opinion. To make the fix fast, include the page address, the exact values you entered, the result you saw, and the result you expected — with a source if you have one. We reproduce it, fix the underlying formula, and pin the corrected value in the automated test suite so the same error cannot come back. If the disagreement turns out to be a difference in convention rather than an error — the two competing formulas for ideal body weight, say, or whether a leap day counts as a whole day — we say so plainly on the page instead of quietly picking a side.
Requesting a calculator
Tell us the calculation and, more usefully, the situation you were in when you needed it. Most of the calculators here exist because somebody described the moment: working out whether an extra R500 a month actually shortens a bond, splitting a restaurant bill where two people did not drink, checking a nurse's due-date estimate against the dates in a diary. The situation tells us which inputs matter and which defaults are sensible, which is most of the design work. We cannot build everything, and we will not build anything that needs your personal data to leave your device.
Questions about a formula
Every calculator states the formula it uses and, where more than one convention exists, which one it follows and why. If a page does not answer your question, ask — the answer usually becomes a new paragraph on that page, because if one person had to ask, the page was incomplete. We are happy to explain the method in as much detail as you want, including the assumptions that make a result an estimate rather than a promise.
Privacy and data questions
The short version is that we hold nothing: the calculations run in your browser and nothing you type is transmitted, so there is no record of your loan amount, your weight, or your due date to request or delete. If you want the longer answer, including what our analytics do and do not see, the privacy page covers it, and questions to the address above are welcome.
Advertising, press and other business
CalcOtter carries a single clearly-labelled advertisement per page, served by a third-party ad network. We do not sell direct placements, publish sponsored calculators, or accept payment for a link in an article — a calculator that quietly favours whoever paid is worthless, and the whole value of this site is that you can check its arithmetic. Press and partnership enquiries are welcome at the same address.
Who runs this
CalcOtter is built and operated by Iris Consulting and Engineering (Pty) Ltd, a private company registered in South Africa. The site is a small, deliberately unglamorous project: static pages, no accounts, no databases, and a rule that every number it prints can be checked by hand. Postal correspondence is not accepted; email reaches us faster and leaves a record we can act on.