Why use BSA instead of weight for chemotherapy?

Body surface area correlates better with metabolic mass than body weight alone, which helps reduce underdosing in small patients and overdosing in large patients for certain chemotherapy protocols.

What if my patient is obese or very thin?

BSA formulas assume typical body condition. In obese patients, consider using ideal body weight or a adjusted constant. In very thin or cachectic patients, verify against your oncology reference and consider protocol-specific adjustments.

How accurate are veterinary BSA formulas?

Veterinary BSA formulas are approximations derived from limited data sets. Accuracy may vary at size extremes. Always verify against your institutional protocol and current oncology references.

Clinical decision support

Body surface area calculator

Estimate body surface area for dogs and cats. Review dose estimates, weight-context interpretation, escalation checks, and suggested next clinical checks. Educational decision-support tool only.

Species Body weight (kg)

BSA formulas use kg. If you enter lb, it will be converted to kg automatically.

Weight unit Drug dose (mg/m², optional)

Educational support only. Verify with clinical judgment and current oncology references.

Edit constants and exponent

K constant (dog) K constant (cat)

Exponent

Defaults are commonly cited references. Adjust to match your oncology protocol or institutional reference.

Body surface area

— m²

Enter patient details

Enter species and weight to calculate BSA.

Weight category —

—

Estimated total dose —

Enter mg/m² dose to estimate total.

Dose verification —

Enter dose to verify.

Clinical next steps

Verify the K constant and exponent with your oncology reference or protocol.
Double-check dose calculation with a second person before administration.
Consider body condition score and whether ideal weight should be used.
Review concurrent medications and organ function that may affect drug handling.
Confirm protocol-specific safety margins and cumulative dose limits.

Safety checks

This tool supports calculation and education only.
It does not diagnose, prescribe, or replace current clinical references.
Verify patient-specific decisions with current formularies, hospital protocols, and veterinarian judgment.
Confirm weight and species are correct before calculating.
BSA formulas are approximations. Verify against your institutional reference.

Basis and limits

Calculation basis: BSA (m²) = K × (body weight in kg)^exponent. Dog K = 0.101, Cat K = 0.1, exponent = 2/3 ≈ 0.6667. Adjustable in the Assumptions panel.
Scope: this tool supports arithmetic. It does not select chemotherapy protocols or determine safety margins.
Before use: verify the formula and constant against your oncology reference.
Total dose: optional mg/m² × BSA calculation is a planning estimate only.

Formula audit trail

Calculation steps will appear here for verification.

Body surface area calculator

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