Embedded Calculator

Every so often I come across some math in an article or story, and more often than not I have some doubt about their results, so I want to check it. This means punching the numbers into a calculator and comparing the results. Since we have all these fancy schmancy computers, I was thinking it would be helpful if someone could come up with a calculator that you could embed in your web page that could verify the writers calculations on the spot. Of course you could still fudge the figures, but you would have to supply your own bogus calculator. And it could be a great help for writers too by giving them a standard format for displaying numerical data and performing the actual computation as well. Something like a miniature spreadsheet might be just the thing:



To be useful, you should be able to change the input value and it should compute the result. This one does not do that. To be really useful, you should be able to change any of the calculated values as well and have it recompute the other values, i.e. it should run forward or backward. The constants and the operations would have to be locked, and somehow the operation that is being performed would have to be shown. A web search for "Embedded Calculator" turned up some results, but they all got rather complicated rather quickly. There is definitely room for improvement here.

Update December 2016 'fixed' embed html.
Update April 2020 evidently I deleted the spreadsheet that was embedded above.