Dogs and cats
Chemotherapy dosing
Body surface area calculator
BSA in m² for dogs and cats, on the standard veterinary formula. The substituted arithmetic is printed under the figure, so the number can go in the record with its working. Free, no signup.
Patient
Result
Enter a patient weight to compute body surface area.
- Working
- 0.101 × kg2/3
- Constant
- k = 10.1 for dogs, on grams. On kilograms that is 10.1 × 100 ÷ 10,000 = 0.101.
This returns BSA only. Per-drug chemotherapy dosing is in the app, where the drug-specific rates, the small-dog dose bands and the citations behind them are maintained.
The working
The formula, and what it does and does not settle
- Formula
BSA (m²) = k × g2/3 ÷ 10,000
Weight in grams, k = 10.1 for dogs and 10.0 for cats, per Price & Frazier (1998). Because 10002/3 is exactly 100, the kilogram form is k ÷ 100 — 0.101 × kg2/3 for dogs and 0.100 × kg2/3 for cats. That is the form this page computes, and the two are the same expression.
- What it settles
Chemotherapy dosing in mg/m², and physiologic scaling
BSA scales sub-linearly with mass, which is why some canine protocols change dose basis below 15 kg rather than applying a blanket reduction — and why that threshold is drug-specific rather than general. Sztukowski (2024, doi:10.1111/jvim.17063) found small dogs on BSA-dosed vincristine were not at increased risk.
- What it does not
Which basis your drug is dosed on
Dose basis is a property of the drug and its protocol, not of the patient. Some agents are dosed per kilogram, and some are published on both bases at rates that are not interchangeable. Read the basis off the protocol in front of you before you use this figure.
In the app
Need the dose this figure feeds, not just the figure?
Workup’s chemo BSA calculator turns this number into a per-drug dose for 5 cytotoxics — Doxorubicin, Vincristine, CCNU (Lomustine), Carboplatin and Cyclophosphamide — each with its published rate and its drug-specific small-dog band where one exists. Where the published rates disagree it takes a position and names it, rather than presenting one figure as settled: the competing value and its attribution are shown beside the dose.
Clinical use
A decision-support tool for licensed veterinary professionals. BSA is one input to chemotherapy dosing among many — verify the dose basis, the rate and the protocol against the patient’s own case before administering any cytotoxic. Workup is not FDA- or USDA-cleared as a medical device.