BSA Dosage Calculator
Calculate a body-surface-area-based medication dose from a patient's height, weight, and the prescribed dose per square metre. The calculator finds the BSA with the Mosteller formula and multiplies it by the mg/m² dose.
Rates and fees change frequently. Always confirm the current figures
with the official authority before relying on this result.
- Educational tool; verify every dose with a clinician and drug reference.
Formula
BSA = √(height × weight / 3600) (Mosteller); dose = BSA × dose per m²
- Many drugs — especially chemotherapy agents — are dosed per square metre of body surface area rather than per kilogram.
- Body surface area is found with the Mosteller formula: the square root of (height × weight ÷ 3600).
- The total dose is then BSA multiplied by the prescribed dose per m².
- Height is entered in centimetres and weight in kilograms; the dose per m² is in milligrams.
- This is an educational tool — every dose must be confirmed with a clinician and the drug's prescribing information.
170 cm, 70 kg, 100 mg/m²
Inputs
- Height: 170 cm
- Weight: 70 kg
- Dose per m²: 100 mg/m²
BSA = √(170 × 70 ÷ 3600) ≈ 1.82 m². Dose = 1.82 × 100 ≈ 182 mg.
Frequently asked questions
What is a BSA-based dose?
It's a medication dose scaled to body surface area (mg per m²) rather than body weight. This is common for chemotherapy and some other drugs.
Which BSA formula is used?
The Mosteller formula — the square root of (height × weight ÷ 3600) — because it's simple and widely accepted in clinical practice.
What units should I enter?
Height in centimetres, weight in kilograms, and the prescribed dose in milligrams per square metre (mg/m²).
Is some chemotherapy capped at a BSA limit?
Yes, some protocols cap BSA (often around 2 m²) to limit dose. Always follow the specific protocol and clinician guidance.
Can I rely on this for prescribing?
No. It's an educational estimate. Verify every dose against the drug reference and with a qualified clinician.
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