Calculator
Body Surface Area (BSA) Calculator for Dogs & Cats — mg/m² Dosing
Body surface area in m² from body weight, and the total dose for drugs dosed in mg/m² (e.g. chemotherapy).
Results are calculated in your browser. Always double-check before administering and use your clinical judgement.
How it is calculated
BSA (m²) = K × (body weight in grams)^(2/3) × 10⁻⁴, with K = 10.1 for dogs [1] and 10.0 for cats [2].
Total dose (mg) = dose (mg/m²) × BSA.
Worked example
10 kg dog → 0.469 m².
Frequently asked questions
What is the BSA of a 10 kg dog?
The Merck Veterinary Manual table gives 0.469 m² for 10 kg, 0.744 m² for 20 kg and 0.975 m² for 30 kg [1].
What K constant is used for cats?
K = 10.0 for cats; for example 4.0 kg is 0.252 m² and 5.0 kg is 0.292 m² [2].
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For veterinary professionals. Information supports — never replaces — clinical judgement; always check the current product label and local regulations.