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DuBois formula steps showing 70 kg, 170 cm giving 1.81 square metres — 70 kg at 170 cm works out to 1.81 m^2, dosing 90 mg at 50 mg/m^2.

Method & verification

How This Tool Works

fact-checked against our calculation methodology

Calculation Method

Computes BSA from Height, Weight and Unit.

Site methodology

BoringToolsKit methodology and verification standard

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Assumptions to Verify

These tools provide general estimates for planning and education only.
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Worked example: 70 kg, 170 cm

Take a 70 kg adult who is 170 cm tall. The DuBois formula multiplies three factors: 0.007184 x (weight in kg)^0.425 x (height in cm)^0.725. Step one: 70^0.425 = 6.0837. Step two: 170^0.725 = 41.4072. Step three: multiply those together, 6.0837 x 41.4072 = 251.917. Step four: 0.007184 x 251.917 = 1.8097, which rounds to 1.81 m^2.

That 1.81 m^2 value matters because many chemotherapy protocols dose per square metre. A regimen calling for 50 mg/m^2 would prescribe about 90 mg for this person (50 x 1.81). Contrast a smaller adult at 50 kg and 160 cm: the same formula gives 1.50 m^2, so the same regimen prescribes 75 mg, a 17% lower dose from a 29% lower body weight. The fractional exponents, not the raw weight, are what compress that difference.

Where BSA dosing breaks down

BSA assumes surface area scales metabolism, which holds reasonably between roughly 1.5 and 2.2 m^2 but degrades at the extremes. Patients above 2.0 m^2 are frequently dosed at a capped BSA of 2.0 m^2 in practice, because trials that established per-m^2 regimens rarely enrolled people that large, so dose-per-area safety data above the cap is thin.

The formula also ignores body composition: two people with identical weight and height can have very different fat, muscle, and organ volumes, which changes drug clearance more than skin area does. This is why carboplatin dosing abandoned BSA entirely in favour of the Calvert equation using glomerular filtration rate. Finally, the tool's own input guard rails (1 to 300 kg, 1 to 250 cm) accept combinations that produce implausible results, such as 300 kg at 100 cm giving about 4.5 m^2, a value outside any validated dosing table. Treat outputs outside the 1.3 to 2.5 m^2 range as flags for clinical review, not usable dose inputs.