In this chapter the relationship between inlet cross-sectional area an tidal prism and the relationship between ebb delta volume and tidal prism are discussed. A physical footing is given for the relationship between cross-sectional area and tidal prism. From this it follows that the relationship is only expected to hold for sets of tidal inlets that are hydrodynamically and geologically similar, implying that they subject to the same long-shore sand transport, have the same sand grain characteristics, have the same type of tide, i.e. semi-diurnal of diurnal and are in a natural state. Examples of cross-sectional area tidal prism relationships for sets of hydrodynamically and geologically similar inlets in the Dutch Wadden Sea and the North Island of New Zealand are presented. From analysis of ebb delta volumes and wave climate, it follows that more sand is stored in the mildly exposed than severely exposed ebb deltas. As an example, the relationship between ebb delta and tidal prism for inlets on the US Coast is presented.