An approach for providing conversion of a planar design to a FinFET design is disclosed. Embodiments include: receiving a planar design having a plurality of diffusion regions; overlapping a plurality of parallel fin mandrels with a plurality of evenly-spaced parallel lines of a grid; snapping the diffusion regions to the grid based on the parallel lines; and generating a FinFET design based on the overlapping and the snapping. Embodiments include the parallel lines and the parallel fin mandrels being perpendicular to a poly orientation associated with the planar design, and determining a spacing length between the parallel lines; determining a plurality of edges of the diffusion regions that are parallel to the poly orientation; and cropping the diffusion regions until each of the edges has a length that is a multiple of the spacing length.