The invention relates to the contactless measurement of a linear textile formation such as yarn, thread, textile fiber, sliver, etc. in which a linear textile formation moves in a radiation flux between a radiation source and a radiation sensor consisting of a plurality of radiation-sensitive elements arranged next to each other in at least one row and in which the diameter and/or the hairiness and/or the density of the linear textile formation is determined on the basis of the number of overshadowed radiation-sensitive elements of the radiation sensor and/or on the basis of the irradiation degree of the radiation-sensitive elements. In order to measure a high degree of the total length of the moving textile formation it is proposed to match the dimensions of the radiation-sensitive elements such that the dimension of the radiation-sensitive elements of the radiation sensor in the direction of the motion of the measured linear textile formation is superior to their dimension in the direction normal to the direction of the motion of the measured linear textile formation.