I find Excel to be a very useful tool for calculating theoretical top speed in each particular gear, and it's possible to determine the theoretical tire diameter (when an obvious tire size isn't available (such as an Enzo (345/35ZR19) versus a Toyota 88C-V (?))) through averaging driven speed in the same gear at different RPMs. Using Excel, and providing a driven tire diameter, I can determine perfect gear splits that allow for the best use of the engine's powerband. Visible gear splits on the sliding scale isn't always enough to satisfy me and when it isn't, I take great satisfaction in knowing I can satisfy myself using a different method. Doubly satisfied, win!