Objective: Careful operative timing is required for children undergoing microtia repair using autologous costochondral grafting. There remains a paucity of data regarding cartilaginous growth of the ribs and synchondrosis routinely harvested during microtia repair. This study employs CT imaging to generate normative costochondral growth curves in children. Method: A population study was performed at a tertiary pediatric hospital. Chest CTs were reviewed in children ages 3 to 20 years. Demographic information was recorded. CT measurements included: cartilaginous length of ribs 6, 7, and 8 and the height of the synchondrosis between ribs 6 and 7. Results: A total of 360 studies were reviewed. At age 6: ribs 6, 7, and 8 measure 5.76 ± 0.65, 7.57 ± 0.87, and 6.68 ± 1.06 cm, respectively. In adulthood ribs 6, 7, and 8 measure 8.29 ± 1.00, 11.10 ± 1.19, and 8.95 ± 1.99 cm. The vertical height of the synchondrosis between ribs 6 and 7 at years 6 and 20 are 2.64 ± 0.37 and 3.59 ± 0.52 cm. Synchondrosis height is 85% and 100% of adult auricle width at ages 6 and 8, respectively. Beginning at 3 years, ribs 6, 7, and 8 grow near linearly at 1.71, 2.46, and 1.35 mm, respectively, per year. Mean synchondrosis growth is 1.81 mm annually. Gender- and race-specific growth charts are presented. Conclusion: Cartilaginous growth of ribs 6 to 8 during childhood is nearly linear. Synchondrosis height approaches adult auricle width at 8 years. Rib size is consistently larger in males and on the left side. These data allow planning for the pediatric otolaryngologist and facial plastic surgeon performing microtia surgery.