Calculating ROI Summary: ROI, or Return On Investment, is an analysis tool used to calculate a project's expected benefit in light of its costs. But it's more complicated than you may think. Learn what it is, when to use it, and how to calculate ROI. July 21, 2005 -- 21:03 GMT (14:03 PDT) Loading... Please wait. Topic: Banking Kick off your day with ZDNet's daily email newsletter. It's the freshest tech news and opinion, served hot. Get it.