Background: Cranial capacity is used as a measure of brain volume and has a relationship with age and gender. The purpose of this study was to provide normative data and population-, age- and gender-specific regression formulae related to cranial capacity using head dimensions among the Ukwuani people of Nigeria. Methods: This study included 605 subjects grouped according to age as follows: 6–12 years, 13–19 years and ≥20 years. A cross-sectional study design using multistage sampling technique was adopted. Head length, head width, and auricular head height were measured in centimetres using a spreading caliper, and cranial capacity was calculated. The data were analysed using SPSS 20. Descriptive and inferential statistics were applied. A t-test was used to identify significant gender differences. Regression analyses were performed to derive age-, gender- and population-specific models. P-values < 0.05 were considered significant. Results: In all the parameters, males had significantly higher values than females (P < 0.05). The mean (SD) cranial capacity values at 6–12 years, 13–19 years and ≥20 years were 1176.95 (98.35) cc, 1288.59 (113.21) cc and 1408.90 (116.44) cc, respectively. Conclusions: All the parameters exhibited sexual dimorphism. Cranial capacity was found to increase with age. The models derived in this work will be relevant to population and growth studies as well as forensic anthropology.