The newly developed system for measuring a contact angle on a sheet was examined to investigate reliability and reproducibility of the measured results. It was clearly confirmed that the automatic contact angle measuring system was much faster and more reliable way to determine the water resistance of a sheet, comparing with Cobb and Stockigt sizing tests. Cobb test showed less significant results with stringently sized sheets, and Stockigt test exhibited the big deviations by discrepancy of the recognition point of coloring according to different testers in spite of explicit test results. On the other hand, the contact angles measured by the automatic system were reproduced with less deviations, irrespectively of different testers. It was interesting to note that the contact angle might be able to used to predict Cobb and Stockigt sizing degree, based upon the high correlation coefficients of 0.95 and 0.97. Hereafter the automatic system will be upgraded to predict Cobb and stockigt sizing degree through the measurement of contact angle.