Playing to the strengths of the internet – an interactive medium* – I think calculators are a really good way of getting people to explore content such that they gain a better understanding of the subject. The best way of seeing what I mean is to have a go – click on either of the examples above, “Rent v mortgage” by the New York Times or the BBC’s Electricity calculator.
*I know that sounds obvious – the internet is interactive – but you wouldn’t think so given the number of static, print graphics being posted on the internet. We’re missing a trick. I’m guessing this is largely due to a lack of skills amongst designers to produce such work. Thankfully this is changing.