BSA Dose Calculator (mg/m² & Pediatric Dose by BSA)

How it works

BSA (Mosteller, m²) = √(height cm × weight kg ÷ 3,600) · dose (mg) = dose (mg/m²) × BSA · child dose = adult dose × BSA ÷ 1.73 m² · Du Bois BSA = 0.007184 × height^0.725 × weight^0.425

Many chemotherapy drugs, some antivirals and several pediatric medicines are prescribed per square metre of body surface area because BSA tracks metabolic rate, blood volume and kidney function better than weight alone across very different body sizes. The Mosteller formula (NEJM 1987) is the simplest and most used; Du Bois is shown for comparison. For children, an adult dose can be scaled by the child’s BSA divided by an average adult BSA of 1.73 m² when no pediatric dose exists. Some regimens cap BSA at 2.0 m² in very large patients, although ASCO advises full weight-based dosing for obese adults with cancer.

Worked example

A patient 170 cm tall weighing 70 kg: BSA = √(170 × 70 ÷ 3,600) = 1.82 m². A drug prescribed at 100 mg/m² therefore needs 100 × 1.82 = 181.8 mg. Scaling a 100 mg adult dose to a child of the same size would give 100 × 1.82 ÷ 1.73 = 105 mg — i.e. the full adult dose.

Sources: Mosteller RD. Simplified calculation of body-surface area. N Engl J Med 1987;317:1098 · Griggs JJ et al. Appropriate systemic therapy dosing for obese adult patients with cancer: ASCO guideline update. J Clin Oncol 2021;39:2037–48

Frequently asked questions