Blood Transfusion Volume Calculator
Whole blood volume needed to reach a target PCV in dogs and cats
Formula & assumptions
Volume (mL) = Weight × k × (Desired PCV − Current PCV) / Donor PCV
k = estimated blood volume constant: 90 mL/kg (dog), 60 mL/kg (cat). These are standard textbook values; some references use 80–90 for dogs and 60–70 for cats, so treat the result as a clinical estimate and reassess PCV after transfusion.
This calculates fresh whole blood. For packed RBCs (typical PCV 60–70%), enter the actual product PCV in the donor field. Aim to transfuse the smallest volume that achieves a safe, not necessarily normal, PCV.
General ceiling: avoid exceeding roughly 22 mL/kg of whole blood in a single episode unless clinically justified, and watch for volume overload in cats and cardiac patients.
Clinical decision-support estimate only. Always cross-match/blood-type where indicated, monitor the patient throughout, and use professional veterinary judgement. Does not replace clinical assessment.