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Body Surface Area Calculator | Du Bois Formula

A body surface area (BSA) calculator estimates total body surface in square metres from weight and height. It uses the Du Bois formula BSA = 0.007184 × W^0.425 × H^0.725 — the most widely referenced BSA equation for chemotherapy dosing, GFR indexing and cardiac output normalisation.

Last updated: September 2026 · Free · No sign-up required

Results

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Quick reference

Reference BSA values (Du Bois):

Height	Weight	BSA
160 cm	55 kg	1.58 m²
170 cm	70 kg	1.80 m²
175 cm	70 kg	1.85 m²
185 cm	90 kg	2.14 m²

medication Dose scaling

Many IV drug doses are written as mg/m² — BSA converts the protocol number into your personal dose.

favorite Cardiac index

Cardiac output divided by BSA gives cardiac index; 2.5–4.0 L/min/m² is the normal adult range.

monitor_heart GFR indexing

Kidney filtration rate is reported per 1.73 m² of BSA so results compare across body sizes.

science Formula spread

Du Bois and Mosteller agree within ~1% for adults; agreement drifts at extremes of paediatric size.

lightbulb A real example — dosing a 70 kg adult

Height 175 cm, weight 70 kg, protocol dose 50 mg/m².

Result: BSA ≈ 1.85 m², so the dose is 50 × 1.85 = 92.5 mg.

What this means: Capping rules (e.g., dose-cap at 2.0 m²) exist because very high BSA correlates more with adiposity than with drug clearance — always confirm against the protocol.

Formula & methodology

Formula: BSA = 0.007184 × Weight(kg)^0.425 × Height(cm)^0.725

The Du Bois formula (1916)

Du Bois & Du Bois fit a linear model to nine subjects' measured surfaces; a century of validation kept it the clinical default. For a 70 kg, 175 cm adult: BSA = 0.007184 × 70^0.425 × 175^0.725 ≈ 1.85 m².

Alternatives: Mosteller √(H×W/3600) gives nearly identical results (±1%) and is easier by hand; Haycock and Gehan-George fit children better. Most adult oncology protocols specify Du Bois or Mosteller explicitly.

Typical adult range: 1.6–2.0 m² (men average ≈1.9, women ≈1.7).

Authoritative source: Mosteller 1987

Frequently asked questions

How is body surface area calculated?

The clinical standard is the Du Bois formula: BSA = 0.007184 × weight(kg)^0.425 × height(cm)^0.725. A 70 kg, 175 cm adult has a BSA of about 1.85 m².

What is a normal BSA?

Most adults fall between 1.6 and 2.0 m². Men average around 1.9 m², women around 1.7 m²; values outside 1.2–2.5 m² are uncommon.

Which BSA formula should I use?

Du Bois for general and oncology use, Mosteller for quick mental math (it agrees within 1% for adults), and paediatric-validated equations like Haycock for small children.

Why is medication dosed by BSA?

Surface area scales with metabolic mass better than raw weight, so cytotoxic drugs dosed mg/m² produce more consistent blood levels across body sizes than mg/kg.

How accurate is the Du Bois formula?

Against modern 3D body scans, Du Bois is typically within 2–4% for average adults — good enough for clinical dosing. It was fitted on just nine subjects in 1916, so accuracy degrades at extremes of size: very tall, very short, or severely obese patients may be better served by Haycock or Gehan–George. Mosteller's simpler formula agrees with Du Bois within about 1% for typical adults.

Is BSA capped for chemotherapy dosing?

Many oncology protocols cap the BSA used for dosing at 2.0 m² (some at 2.2), because beyond that point extra surface area correlates more with adiposity than with drug clearance, and uncapped dosing can mean overdosing obese patients. Capping rules are protocol-specific — always follow the regimen's own guidance rather than the raw calculator output.

Can children use the same BSA formula?

Du Bois works reasonably for children, but paediatric-validated equations like Haycock (0.024265 × W^0.5378 × H^0.3964) or Gehan–George fit children's proportions better. Neonatal and infant dosing often uses weight-based or allometric scaling instead. If the protocol names a formula, use that one — consistency with the trial data matters more than theoretical accuracy.

What is BSA used for besides drug dosing?

Cardiac index (cardiac output divided by BSA) lets doctors compare heart function across body sizes; GFR is reported indexed to 1.73 m² of BSA; burn size uses BSA percentages (the 'rule of nines'); and some basal metabolic rate equations normalize to surface area. In each case BSA is a size-normalizer, not a diagnosis by itself.

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