It is well known that light scattering by nanometric pores is adverse to realize a high transparency in ceramics; however, a suitable model that gives this phenomenon a quantitative evaluation is still lacking. In this work, a simplified model based on Rayleigh's theory was developed in order to unravel the light scattering by nanometric pores, taking polycrystalline KNNB‐xSm ceramics with high transparency (>67% at 780 nm) as example. The validity of this model was further verified by its good agreement with experimental results. Based on detailed simulations, we came to the conclusion that the pore volume fraction p is a more important parameter on the transparency of KNNB‐xSm ceramics than pore size dpore. Our findings in this work might provide inspiring insight to obtain highly transparent KNN‐based ceramics and more. [ABSTRACT FROM AUTHOR]