Know-How Exchange : E-Marketing

It all depends on the perceived value for the user. If what you're calculating can't be gotten anywhere else in the world, and what you offer is extremely trustworthy and valuable, then the number of questions isn't a big deal. If you're offering a calculation that's easily obtainable elsewhere, then if you can offer the same results with fewer inputs, you have an advantage.

The answer varies for each specific application and for individual users. The value may be high for one user (who may not be skilled enough to figure out the math) and low for another (who knows the math already).

The best approach may be to try a few alternatives -- 3, 5 and 7 inputs, for example -- and see how many site visitors stick around for each. Also see how many are converted for each. And each test can be specific to a particular industry, product/service category and end-user channel.

The beauty of these kinds of questions is that they can be answered/tested quickly and easily for not-too-much money.

While you are at it, remember that the benefit promise and specific offer/copy approach are also big influencers, so maintain some consistency and minimize the number of variables. (May want to draw on expertise from a market research professional.)