There are lots of results out there for the query 'large type calculators' but surprisingly few online examples. Most of the search results are for physical calculators for purchase. Which seems kind of surprising. Using a little Javascript and a little CSS it's pretty easy to create a working large type calculator. Hopefully this will be of some use to low vision web users out there.
As for the implementation details, this is yet another JavaScript plus CSS plus python tool hosted on app-engine and iframed into blogger. The underlying Javascript is the same as that used for the piulator and the layout is modified through the CSS. Which is to say expect a few more calculator posts before a slightly more detailed step through of the code specifics.