Carsharing is a transportation alternative that helps to fill the gap between public transportation and private vehicle ownership, encouraging reduced vehicle ownership and use and increasing the sustainability of a carsharing member's travel choices. This paper provides methodologies to determine potential carsharing members, particularly for free-floating carsharing systems which are among the fastest-growing types of carsharing operations. It also provides innovative techniques to determine the number of trips taken and the share of total travel completed with carsharing. Using widely available Census and demographic data to predict, an analyst can predict the size of the potential membership base and the trip generation likelihood, given the carsharing organization’s operational characteristics. For a free-floating system, the size of the operating area is a key determinant in membership prediction. Other significant variables include age distributions, household sizes, household densities, and proportion of area residents working outside the home. For trip generation, average household income and size have a negative effect on modal split and trip generation, but land use density has a positive effect. These methodologies are likely to be valuable to both carsharing and metropolitan planning organizations.