Abstract The compaction behaviour of nano-sized zirconia powders prepared by the coprecipitation method was studied by means of pore size distribution measurements and density versus pressure relation determination. Agglomerate strength can be characterized with the determination of pressure dependence of compacted density and pore size distributions of compacts. By combining these two techniques it was found that there were two strength points for agglomerates: one of lower pressure at which agglomerates began to fragment and another one of higher pressure at which agglomerates were fully fragmented. The strength point for complete agglomerate fragmentation was much more useful for characterizing the properties of agglomerates.