The initial version of the resistance calculator is now added to the website. The calculator is applicable for most types of ship hulls that sail in the displacement mode, without deeply immersed transoms. For the prediction of ship resistance in the preliminary stages of the ship design process, naval architects often use methods that are less complex and expensive than CFD simulations and experiments. Michell's thin ship theory can be used to quickly evaluate wave-making resistance, although, the original theory gives poor estimates for conventional hulls. In this calculator, techniques to improve the theory are introduced that account for viscous and non-linear effects. The improvements are validated by numerical simulation on profoundly different hull forms.