the yarns 2 and the concentration c of the sizing liquid by using a formula where ws is the weight of the sizing liquid carried away by the yarns 2 and ww is the weight of the yarns 2 processed for sizing in the description of the first and second embodiments of the present invention it is supposed for simplicity that the concentration c of the sizing liquid 9 contained in the cavity box 11 remains constant after steam is supplied into the cavity box 11 the weight ws of the sizing liquid taken up by the yarn 2 is a function of the sizing liquid consumption q the specific gravity u03c1 of the sizing liquid and the concentration c of the sizing liquid and the weight ww of the processed yarns 2 is a function of the length yards of the processed yarns 2 the number n of the yarns 2 the count cotton count e of the yarns 2 and constants 840 and 2 2 therefore a sizing machine in a second embodiment employs a flowmeter for measuring the flow rate of steam 18 as shown in fig4 a flowmeter 32 such as a piezoelectric digital flowmeter or an electromagnetic flowmeter and a pressure sensor 33 are provided after an operating device 16 with respect to the direction of flow of steam an integrator 27 calculates the total quantity u03c3q.