A work machine loads materials onto a conveyance vehicle. The work machine includes a work implement having a bucket, a topography sensor configured to measure a topography and a controller. The controller determines a target digging path of the bucket based on topographical data indicative of the topography measured by the topography sensor. The controller acquires an actual digging path based on positions of the bucket during digging. The controller is calculates at least one of a viscosity and a hardness of materials based on a difference between the target digging path and the actual digging path.