Blood Transfusion Volume Calculator
Whole blood volume needed to reach a target PCV in dogs and cats
Which patient are you transfusing?
The species sets the blood volume constant (k) the formula uses.
Enter the weight and PCV values
The volume recalculates as you type — nothing to submit.
Transfusion volume
The volume, its working and any warning update as you type.
Your transfusion volume will appear here
Enter the patient's body weight, current and desired PCV, and the PCV of the blood being given — the volume recalculates after any change.
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.
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.
