The present invention relates to a method and an arrangement for measuring the smoothness of grains. In one embodiment, the arrangement includes a channel for supplying grains, especially rice grains, an obstacle arranged at the channel to slow down grains falling on the obstacle, so that the flow of grains forms a heap on the obstacle and an image capturing device placed facing the obstacle. The image capturing device is arranged to capture an image of the heap, where the area under the curve of the captured heap image indicates the degree of smoothness of the grains or the course of the curve of the captured heap image indicates the degree of smoothness of the grains.