The article discusses the process of obtaining fibrous material from a thermoplastic by blowing methods, and also provides a method for calculating the average diameter d(f) and length l(f) of elementary fibers. According to the presented calculations, the average elementary fibers' diameter value d(f) depends on the airflow speed from the blow head in the fiber formation zone. The greater the air velocity V-p, the smaller the diameter of the elementary fibers. The elementary fibers' length l(f) depends on their diameter d(f) and variable angle gamma of the blowing head diffuser. The smaller the diameter of the elementary fibers df and the larger the variable angle gamma, the smaller the length of the elementary fibers. At gamma = 0 degrees, the fiber is obtained, with an increase in the angle gamma, the fiber length becomes fixed. The average elementary fibers' diameter d(f) varies depending on the speed of the airflow flowing from the blowing head in the fiber formation zone. The greater the air velocity V-p, the smaller the diameter of the elementary fibers. The discrepancy between the calculating results of the average fiber diameter with their real values does not exceed 13%, which, according to the process complexity, can be considered satisfactory. The elementary fibers' length l(f) depends on the elementary fibers' diameter d(f) and a variable angle gamma. The smaller the diameter of the elementary fibers d(f) and the larger the variable angle gamma, the smaller the length of the elementary fibers. At gamma = 0 deg, the infinite length fiber is obtained, and with an increase in the angle., the fiber length becomes fixed.