The capability of projecting a military force on land, from ships located at a safe distance from the shore, without the need of using existing infrastructure such as ports, is unique and important. It is important because such operations from the sea provide great flexibility in where on land to insert the military force. However, modern weapons are an imminent danger to amphibious ships that are located near the shore. The obvious solution is to increase the ship-to-shore distance, but that also means that it will take longer to transport the landing force to the shore. Vehicles and heavy equipment have to be transported by landing craft, and making landing craft faster without affecting the condition of the people on board, especially in adverse weather, is not straightforward. What would be the best trade-off between ship-to-shore distance and time? As illustrated by this example, the design process of amphibious ships – and the connectors that they carry – is characterised by finding an acceptable balance between the different factors that determine the operational effectiveness of the operation. The tool presented in this paper is intended to be used early in the design process. It estimates operational effectiveness by modelling the interaction between several factors: (a) the composition of the landing force: number of personnel, number of vehicles, amount of equipment, smallest unit of action; (b) the characteristics of the connectors: payload capacity, speed, number of connectors; and (c) the operational requirements: number of waves, ship-to-shore distance, and time. The tool is based on a set of analytical equations and is capable of solving these for any combination of two factors or variables. For example, the tool can estimate number of waves and time (amphibious operation planning data) or alternatively, payload capacity and speed (connector design data). The analytical tool presented in this paper provides insight that is essential to the design of effective amphibious ships and connectors. The paper will show several applications, including comparing the wave characteristics of connectors (different types of landing craft and helicopters) and simulating a non-combatant evacuation operation (NEO) for which a mix of different types of connectors are used. There is a need for this tool because amphibious operation requirements are often conflicting – for example ship-to-shore distance and time – which makes it difficult to find an acceptable balance between operational effectiveness, technical feasibility and affordability. Technical feasibility and affordability are not part of the analysis, but can be included in the results without great difficulty.