A numerical analysis on strength of placed block revetments in dike constructions is presented. A 3 dimensional finite element model is developed with physical and geometrical nonlinear characteristics for a very commonly used type of placed block revetment in the Netherlands. Earlier research showed that clamp-ing forces can have a relevant positive contribution to the strength of block revetments in dike constructions. But adopting these clamping forces in strength-calculations of dike constructions is still not standardized be-cause the relation between results from field-tests and wave loads is missing. To this end both field-tests and calculations of failure of the revetment caused by wave attack are numerical simulated. The general behavior of the model in both calculations is described and explained. A brief outline of parameter studies is given. The result is a relation between the strength measured during field-tests and failure in practice under wave attack.