A work vehicle includes a work implement. A control system for the work vehicle includes a controller. The controller obtains first topographical data indicative of a topography of a work target before filling work. The controller obtains blade tip position data indicative of a blade tip position of the work implement during the filling work. The controller obtains second topographical data indicative of a compacted topography after the filling work. The controller determines a compression rate of the work target from the first topographical data, the blade tip position data, and the second topographical data.