Contact
This site is maintained by one person, so replies are not instant — but every message is read, and corrections are prioritised.
The fastest way to reach us is by email:
Reporting an error
A wrong formula produces a confidently wrong number, which is the worst failure mode a calculator can have. If a result looks incorrect, please include as much of the following as you can — it makes the difference between a fix in a day and a fix in a week:
- Which calculator, and ideally the page address from your browser's address bar.
- The inputs you entered. If the address bar contains
?followed by values, sending that link gives us your exact inputs. - The result you got, and roughly what you expected instead.
- If you can, what you believe the correct answer should be and why.
Every calculator page states its formula, variables and assumptions near the bottom. If you think the issue is an assumption rather than the arithmetic — for example that a threshold or a rate is out of date — say so, as that is usually a quicker fix.
Requesting a calculator
Suggestions are welcome, and the most useful ones describe the decision you are trying to make rather than just the tool name. Tell us what you were trying to work out and what you had to do instead — that is what tells us whether a calculator would actually help.
Questions about a result
We can explain how a specific calculation works and what it assumes. We cannot tell you what you should do, and we cannot review your individual financial, tax or construction situation. For that you need a professional who can see the whole picture — see the disclaimer for the limits of what these tools provide.
Privacy and data
Emailing us is the only way information reaches us. The calculators themselves run in your browser and nothing you type into them is transmitted or stored. See the privacy policy for details.
Advertising and partnerships
Enquiries about advertising placements or partnerships are welcome via the address above. Note that calculator results are fixed in code and are not adjustable by any partner or advertiser — see the disclaimer.