Which BSA formula should I use?

Mosteller is the most widely used because it is simple and accurate across adults and children. DuBois is the historical standard, and Haycock is often preferred for small children and infants. Most protocols specify which formula to apply.

How is the Mosteller BSA calculated?

Mosteller BSA in square metres equals the square root of height in cm multiplied by weight in kg, divided by 3600. For a 170 cm, 70 kg patient that is the square root of 11900 over 3600, about 1.82 square metres.

Why would I cap the BSA at 2.0?

Some regimens, such as certain capecitabine and carboplatin protocols, cap BSA at a value like 2.0 square metres to avoid overdosing large patients. The tool has an optional cap so the dose uses the smaller of actual or capped BSA.

Does this replace a pharmacist check?

No. This is an educational aid. High-alert and cytotoxic doses must be independently verified against the protocol, the prescribing information, and a second qualified clinician before any drug is given.

Is any patient data sent anywhere?

No. All arithmetic happens locally in your browser. Height, weight, and dose values are never transmitted or stored on a server.

What is the Drug Dose by BSA Calculator?

Calculate drug doses from body surface area using Mosteller, DuBois, or Haycock BSA formulas and a mg/m2 parameter. For oncology, pediatric, and high-alert dosing. Runs entirely in your browser. It runs free in your browser on Gera Tools, with nothing uploaded.

Drug Dose by BSA Calculator

Name: Drug Dose by BSA Calculator
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

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Many specialty drugs, especially cytotoxic chemotherapy agents, are dosed per square metre of body surface area rather than per kilogram. This calculator computes body surface area (BSA) from height and weight using three validated formulas and multiplies by your mg/m² parameter to give a total dose.

Why BSA-based dosing?

Body surface area correlates better than body weight with many physiological variables — including cardiac output, blood volume, and hepatic clearance — that govern how cytotoxic agents are distributed and eliminated. Dosing by BSA aims to achieve a more consistent drug exposure (area under the curve) across patients of different sizes, which is critical for drugs with narrow therapeutic indices where under-dosing reduces efficacy and over-dosing causes serious toxicity.

The three formulas

Mosteller: BSA = sqrt( height_cm × weight_kg / 3600 )
DuBois:    BSA = 0.007184 × height_cm^0.725 × weight_kg^0.425
Haycock:   BSA = 0.024265 × height_cm^0.3964 × weight_kg^0.5378

Mosteller is the most widely adopted in oncology practice because of its computational simplicity and good agreement with other methods across adult body sizes. DuBois is the historical standard, published in 1916 and embedded in many older protocol reference documents. Haycock was validated specifically against infants and children, where the other formulas are less precise.

Worked example

A patient is 170 cm and 70 kg:

Mosteller BSA = √(170 × 70 / 3600) = √(3.306) ≈ 1.818 m²
DuBois BSA ≈ 0.007184 × 170^0.725 × 70^0.425 ≈ 1.823 m²

A protocol ordering 75 mg/m² (Mosteller) gives: 75 × 1.818 ≈ 136 mg

The two formulas agree to within 0.3 m² here, but for a large or obese patient the difference can be clinically meaningful.

BSA capping

Some protocols specify that BSA used for dosing should not exceed a cap value — commonly 2.0 m² — to limit the total dose in very large patients and avoid toxicity that scales faster than BSA at extremes. When a cap is specified, the tool uses the lesser of the calculated BSA or the cap before multiplying by mg/m².

Important limitations

This tool is for educational use and independent double-checking only. High-alert and cytotoxic drugs must be independently verified by a qualified pharmacist against the written protocol and prescribing information before any dose is prepared or administered. The three formulas show approximations and can diverge in obese patients, children, or those with oedema; consult the protocol for the intended formula. No patient data is transmitted — all arithmetic runs locally in your browser.