How much blood is there in 1 transfusion?

One unit of whole blood contains approximately 450 millilitres (mL) of blood. This volume can vary slightly, typically between 400 and 500 mL. It's important to note that during a blood transfusion, the recipient may not receive the entire unit of whole blood. The volume transfused and the number of units required depend on various factors, including the patient's condition, blood loss, and haemoglobin levels.