Small-angle X-ray scattering (SAXS) is a powerful and rapid technique for obtaining structural information from materials as well as qualitative and quantitative assessments of porosity. However, the use of SAXS for investigating the porosity of materials is not widespread, and nitrogen adsorption measurements are the standard method. In this study, a range of undoped and rare-earth doped ceria-zirconia materials with the general formula CexZr1-x-yREyO2-δ (RE = La, Y, Nd, La-Nd) have been synthesised, and their pore size characterised using both lab and synchrotron SAXS. Previously, it was shown that porous properties, calculated by nitrogen adsorption, were important for the final oxygen storage performance of this class of materials. Herein we demonstrate that the average pore size and the pore size distributions can be extracted by using an easy to use, fast and adaptable Monte-Carlo method for fitting the experimental SAXS patterns. The values obtained from SAXS agree with values extracted from nitrogen adsorption measurements, demonstrating the potential of SAXS for measuring these properties across an array of materials. The pace of collecting and analysing the data makes SAXS a compatible technique with high-throughput materials discovery where pore size and porosity is a key property. This method is generalizable and can be easily implemented in other cases of porous materials.