The Maximum Allowable Blood Loss (MABL) is a clinical calculator designed to estimate the maximum volume of blood that a patient can lose during surgery without requiring a blood transfusion. The MABL is calculated based on the patient's initial hemoglobin level, the lowest acceptable hemoglobin level (usually set at 6 g/dL), and the patient's estimated blood volume. 

This calculator is applicable to all patient populations undergoing surgical procedures, particularly those at high risk for significant blood loss. It aids clinicians in planning for potential blood loss during surgery, managing perioperative blood transfusion, and optimizing patient safety. 

However, the MABL should not be used in isolation to guide clinical decision-making. It does not account for individual patient factors such as comorbidities, tolerance to anemia, or the presence of ongoing bleeding. Therefore, clinical judgment should always be used in conjunction with the MABL to determine the need for blood transfusion.