A machine for controlling the shape of a reel of web product, comprising at least one pick-up zone (12A, 112A, 112A') for at least one reel to be evaluated, a moving apparatus for moving said at least one reel along a moving path from said pick-up zone (12A, 112A, 112A') toward an unloading zone, and an evaluation apparatus for evaluating one or more geometric parameters of the reel, said evaluation apparatus being configured to act in at least one evaluation zone provided at least in part along said moving path of the reel, wherein said evaluation apparatus comprises at least one distance sensor (21, 22, 321, 322), wherein during a relative movement of the reel with respect to the distance measurement sensor (21, 22, 321, 322), said distance measurement sensor (21, 22, 321, 322) is adapted to read the respective distance from the reel, wherein said evaluation apparatus further comprising a device for detecting the position of the reel, in the direction of relative movement, with respect to said distance sensor (21, 22, 321, 322), so that for each distance reading carried out by a distance sensor the relative position of the reel in said direction of movement is also known, characterized in that the combination of the distance information acquired by the distance sensor (21, 22) from the reel and of the information relating to the position of the reel in the direction of movement allows information on the geometry of the reel to be obtained, wherein said machine comprising a regulation device (123, 223) for regulating the position of said at least one distance sensor (21, 22, 321, 322) in the evaluation zone of the reel, said regulation device (123, 223) comprising at least one regulation direction of the position of the sensor, wherein said position regulation device (123, 223) further comprising a further device for indicating the position of the distance sensor (21, 22, 321, 322) along said regulation direction. wherein said evaluation apparatus comprises at least one distance sensor (21, 22, 321, 322), wherein during a relative movement of the reel with respect to the distance measurement sensor (21, 22, 321, 322), said distance measurement sensor (21, 22, 321, 322) is adapted to read the respective distance from the reel, wherein said evaluation apparatus further comprising a device for detecting the position of the reel, in the direction of relative movement, with respect to said distance sensor (21, 22, 321, 322), so that for each distance reading carried out by a distance sensor the relative position of the reel in said direction of movement is also known, characterized in that the combination of the distance information acquired by the distance sensor (21, 22) from the reel and of the information relating to the position of the reel in the direction of movement allows information on the geometry of the reel to be obtained, wherein said machine comprising a regulation device (123, 223) for regulating the position of said at least one distance sensor (21, 22, 321, 322) in the evaluation zone of the reel, said regulation device (123, 223) comprising at least one regulation direction of the position of the sensor, wherein said position regulation device (123, 223) further comprising a further device for indicating the position of the distance sensor (21, 22, 321, 322) along said regulation direction.