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Found a calculator giving the wrong answer? That is the message we most want to receive.
Before you write
If you are reporting a wrong result, please include the exact numbers you entered and what you expected instead. A reproducible example is the difference between a fix today and a fix never. If your university or institution publishes a different conversion formula from the one we use, a link to it helps enormously.
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Messages are read by a person, not a bot. Reported calculation errors are prioritised over everything else. We do not add anyone to a mailing list, and we do not pass your address on.
This page was last reviewed on 11 August 2026.