There are many reports saying that the trial results of supertankers, which have been built in recent years, show much smaller power than the tank test prediction. Main reason of the trend may be due to deficiency of the method of residual resistance. The authors try to develop a new method of correlation between models and ships. The method is based on the assumption that the flow fields around models and ships are similar to each other including their boundary layers, and only their thicknesses are different according to their respective Reynolds numbers. Thus the form effects on frictional resistance become linearly proportional to the corresponding plane friction, viz. they follow the law of Reynolds instead of Froude. This is a result similar to the Hughes proposal, except that in the case of actual ships the value of plane friction should be corrected by the roughness allowance. The formula of prediction of the effects between ships and models is C_F8 = C_Fm × C_fp8 +Δ C_f / C_fpm Applying the method to some results of supertankers, reasonable explanation for property of resistance is gained as seen in Figs. It is hoped that queer phenomena as negative Δ C_f may be removed by the use of this method. A method of estimation of the form effects for fuller ships like tankers is also proposed. Comparison of the calculated figures with the tank tests shows a close agreement. The method assisted by the use of Taylor chart may be convenient to initial designers.