The Blood Volume Calculator provides quick estimates of total blood volume (TBV) using two common approaches. The simple method multiplies body weight by a guideline value (commonly ~75 mL/kg for males and ~65 mL/kg for females) and is frequently used in anesthesia and clinical practice for rapid estimates. The Nadler formula is an individualized equation that uses height and weight to estimate TBV more precisely and is widely cited in physiology literature. If you input hematocrit (Hct), the calculator also returns plasma volume = TBV × (1 − Hct). Results are approximate — for clinical decisions (drug dosing, transfusion planning, research) use measured values or consult healthcare professionals.