The aim of this study is to examine the relationship between the wave steepness (Hi /L) with a stable profile slope of small size stone rubble mound breakwaters. The results of the study are expected to solve the difficulty of getting a big size crushed stone as a required based on Hudson method. Laboratory physical model study under 1:20 geometric scale was performed. The results showed that the initial sloping breakwater was changed into the S Curve shape profile and achieve a stable condition on the profile equation of y = �ax3 �bx + c, where a, b and c are the factors which are functions of dHi/L2. Factor c is a relative depth (d�/d). The Equations obtained can be used in the planning and designing of S-Curve rubble mound breakwater with relatively small grain size of rocks. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021.