PURPOSE: To provide a method for determining the size of stitch loops, therefore, for determining the degree of transverse elongation of socks in sock-high speed production machines.

CONSTITUTION: A control unit stores two pairs of values including the height of stitch-formation triangles and corresponding width of the knitted socks regarding the respective types and kinds of yarns to form each of plural zones of socks and, if needed, the specific length and corresponding width of the knitted socks and, if needed, the height of the stitch-formation triangles and corresponding specific length of the knitted socks. The width and type of a yarn are selected for each zone to be produced, and the height of the stitch-formation triangle for each zone is determined by a control unit by means of an equation which represents a straight line. The number of turns and angular position of a needle cylinder are measured and fed to the control unit which then sends signals to step motors.