Background: Autogenous fat grafting (AFG) is a well-known procedure utilized in addition to breast augmentation (BA) to improve breast appearance. Plastic surgeons usually estimate the ideal AFG volume relying on their personal experience based on similar previous cases: inaccurate predictions could result in incorrect evaluation of donor sites and even needless fat transfer. The purpose of this paper is to describe and prove the validity of our surgical technique and provide a simple and easy-to-use mathematical formula to assess the adequate proportion, between the volume of the implants and of the AFG, in order to obtain a natural shape and a proper volume in BA.Methods: One hundred and twenty-two patients (244 breasts) were subjected to primary/secondary hybrid BA (HBA). A formula was utilized to assess the volume of fat graft. Data about their age, body mass index (BMI), incision and implants were collected. Follow-up for analysis was fixed at less than 15 days, 1, 3, 6 and 12 months for analysis. Preoperative photographs were compared with postoperative at 12 months. Pre and postoperative Breast-Q © were administered to every patient. A statistical analysis was performed comparing Breast-Q © preoperative means with postoperative ones through t-student test. We globally defined the patients as follows: "very dissatisfied" if total score 0-25; "somewhat dissatisfied", score 26-50; "somewhat satisfied", score 51-75; "very satisfied", score 76-100.Results: All patients received Ergonomix-style Motiva Smooth/SilkSurface with low/high projection (range, 120-225 mL, mean 170 mL) and an average AFG volume of 600 mL (range, 480-720 mL). Breast-Q © analysis showed a statistically significant difference between preoperative and postoperative modules. 122 (100%) patients were "very satisfied". Thirteen cases of complications presented in 12 patients (10.65%): 5 hypertrophic scarring (4.09%), 3 wound dehiscence (2.46%), 3 hematomas (2.46%), 1 seroma (0.82%), 1 fat necrosis (0.82%).Conclusions: Our surgical technique proves low complication rate and short recovery times. Our mathematical formula to calculate the AFG seems to be both predictive and a precise guide for surgical decision-making in planning the treatment of patients candidated for HBA. In fact, the analysis of Breast-Q © questionnaires shows a high grade of satisfaction among patients. Further investigations should be performed in order to study a wider population and different type of implants.