Large burns excision and graft can produce major blood loss. The main objective of this study is to evaluate the blood loss in relation with the excision size in square centimeters (cm2) in adults. We conducted a monocentric, observational, prospective and open study in a burn intensive care unit. Patients aged-over 18 with burn wounds excision and autografting covering at least 5% of total body surface area (TBS) were enrolled. Blood loss was evaluated with Mercuriali formula. 139 procedures were evaluated: median graft size was 1637cm2, median blood loss was 0.8ml/cm2 excised and grafted skin and median total blood loss was 1444ml. 84 procedures (i.e. 60.4%) required transfusion. 66 procedures concerned upper limbs, 75 lower limbs, 17 head and 72 trunk. 126 procedures used tangential excision, 10 used fascia excision and 3 used the two techniques. Patients with comorbidities (ASA score 3 or 4) had more bleeding (p=0.001). The results that were obtained, i.e. approximately 0.8ml/cm2 of excised and grafted skin, are similar to those of other published studies, which concerned specific populations such as pediatrics. Determining blood loss in one centre can help physicians to calculate the excisable area without any transfusion. However, blood loss can vary widely between patients and one must consider individual clinical situation to provide safe surgery.