A seat and motorized stem fit device is designed for fitting a cyclist on a bicycle having a seat post and a seat, with the seat post being an original seat post provided by a seat post manufacturer. The motorized seat post fit device comprises a drive assembly and an adjustable seat assembly coupled to the drive assembly and providing an interface between the seat post and the seat. The drive assembly controls the adjustable seat assembly to provide at least one of a vertical displacement and a horizontal displacement of the seat relative to the seat post.