An engineering scaling process is applied to the solid breeder ITER TBM designs in accordance with the testing objectives of validating the design tools and the database, and evaluating blanket performance under prototypical operating conditions. The goal of scaling is to ensure that changes in structural response and performance caused by changes in size and operating conditions do not reduce the usefulness of the tests. Initially, constitutive equations are applied to lay out the basic operating and design parameters that dominate blanket phenomena. The suitability of these similarity criteria for the TBM design is then confirmed by comparing finite element predictions of prototype and scale model responses. The TBM design also takes into account the need to check the codes and data for future design use. Specifically, predictability of tritium production and nuclear heating rates in a complex geometry, tritium release and permeation characteristics under fusion environments belong to this category. We conclude that this engineering scaling design process has maximized the value of ITER testing.