When the impact of an aggregate's structure on its physical properties is adequately accounted for, it is possible to use those properties for quantifying the structure. A recent paper [1] has discussed such structure-property-relationships for pyrogenic powders. Based on them a calculation scheme is proposed that allow the analysis of size distributions from Dynamic Light Scattering (DLS) and Optical Centrifugation Analysis (OCA) with regard to the translational hydrodynamic diameter, the diameter of gyration and the aggregation number. The scheme includes the conversion from optically weighted to number weighted distributions. The performance of this calculation scheme is tested for different grades of fumed silica, which were analyzed by two DLS and one OCA instrument. A fairly good agreement is observed with regard to medians of the distribution functions. The paper shows that differences in size distributions obtained by different measurement techniques may not only explained qualitatively but can even quantitatively traced back to distribution functions of structural aggregate parameters.