Consonant inventories are commonly drawn to assess the phonological acquisition of toddlers. However, the spontaneous speech data that are analysed often vary substantially in size and composition. Consequently, comparisons between children and across studies are fundamentally hampered. This study aims to examine the effect of sample size on the resulting consonant inventories. A spontaneous speech corpus of 30 Dutch-speaking 2-year-olds was used. The results indicate that in order to construct and compare inventories reliably, they should be drawn from speech samples that are equally large. A new consonant inventory procedure is introduced. The implementation of this procedure demonstrates considerably less variation in inventory size across children and word positions than reported previously. This finding has important implications for clinical studies that constructed and compared inventories of typically and atypically developing children without normalizing the sample size.