Breast cancer is the most commonly diagnosed cancer worldwide and is the leading cause of cancer-related death in more than 100 countries. Breast cancer surgery, especially when it involves a mastectomy, is associated with unaesthetic results that can be traumatic. Therefore, breast reconstruction is crucial for the patient to return to normal life, avoiding the psychological consequences. Based on free tissue transfer with microsurgery, autologous breast reconstruction is the gold standard for breast reconstruction, especially in irradiated patients. To plan the reconstruction surgery and locate the cutaneous perforating vessels supplying blood to the flap, preoperative Computed Tomography Angiography (CTA) is usually performed. However, only approximate and qualitative measurements are obtained and the location of the umbilical perforators reported by the radiologist. This paper advances a quantitative method to assess autologous Deep Inferior Epigastric Perforator (DIEP) flap volume and thickness from CTA images. This method is validated by measuring flap volume intraoperatively in the operating room of the Hospital Universitari de Bellvitge. These measurements could improve preoperative planning by reconstructive surgeons as they would know beforehand whether the amount of adipose tissue that can be harvested is sufficient to reconstruct the breast completely. This information could be crucial in thin and large breasted women or if bilateral breast reconstruction is planned.