Background: This study aimed to establish normative breast volume data for women of varying ages, body masses and breast sizes, and to determine the effect of age and body mass index (BMI) on breast volume. Methods: The breast volume of 356 women (age range: 18.1–83.7 years; BMI range: 18.4–54.5 kg/m²) was measured using three-dimensional scanning in a prone position. Results: Breast volumes ranged from 48 to 3100 mL. Although breast volume was not significantly affected by age, it was significantly affected by BMI, with the breast volume of overweight and obese women being two-to-three times greater than women with normal BMI’s. Conclusion: It is recommended that bra cups must be designed to support the wide range and increasing magnitude of breast volumes exhibited by women. Practitioner summary: This original research provides evidence for bra designers and manufacturers on the range of breast volumes of women and the significant effect of BMI on breast volume. Bra cups need to be designed to support the wide range and increasing magnitude of breast volumes exhibited by women.