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Body Surface Area Calculation Formula
Mosteller, DuBois & DuBois, and Haycock explained — how to calculate BSA from height and weight, with a worked example and dosing context.
How to calculate body surface area
The primary clinical body surface area calculation formula is Mosteller (1987): BSA (m²) = √[(Height(cm) × Weight(kg)) / 3600]. Enter height in centimetres and weight in kilograms; the result is BSA calculation in m². Prefer our body surface area calculator for Mosteller, DuBois, and Haycock side by side.
Body surface area (BSA) is an estimate of the external surface of the human body in square metres (m²). Clinical BSA is calculated from height and weight — not by measuring skin directly.
Height + weight → BSA result
How is body surface area calculated from anthropometrics.
Typical adult BSA range
Approximate adult values (m²) for orientation only.
*1.73 m² is the standard indexing constant used when reporting eGFR in mL/min/1.73 m².
What you need before you calculate BSA
BSA calculation from height and weight needs only two measured values. This is how to calculate body surface area from height and weight (or from weight and height — order does not change the product):
- Height in centimetres (cm) for the standard body surface area formula kg and cm
- Weight in kilograms (kg)
If you have inches and pounds: height (cm) = inches × 2.54; weight (kg) = pounds ÷ 2.2046. A historical body surface area nomogram plotted the same inputs graphically; modern practice uses the equations below (or a calculator).
Mosteller formula BSA (primary)
The Mosteller body surface area formula (Mosteller RD, N Engl J Med 1987) is the simplest bedside BSA formula and the method most clinicians use to calculate body surface area Mosteller by hand.
DuBois and DuBois body surface area formula
The classic DuBois formula BSA (Du Bois & Du Bois, 1916) is still referenced on many labels and remains the historical standard when you calculate body surface area DuBois.
Haycock formula BSA (pediatrics)
The Haycock body surface area formula (Haycock et al., 1978) was validated across infants, children, and adults and is often preferred for how to calculate body surface area in pediatrics and body surface area for pediatric dosing.
Gehan and George & Boyd formulas
The Gehan and George formula BSA (1970) is: BSA (m²) = 0.02350 × Height(cm)0.42246 × Weight(kg)0.51456. The Boyd formula body surface area (1935) uses a logarithmic weight term and appears less often at the bedside; our BSA calculator can show Boyd alongside Mosteller and DuBois when you need a cross-check.
BSA calculation step by step (Mosteller)
This is body surface area calculation manually — how to calculate BSA and how to calculate m² body surface area with Mosteller:
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Step 1 — Measure height and weight. Standing height in cm; weight in kg. For nursing workflows, confirm the same units used by the protocol.
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Step 2 — Convert units if needed. Inches × 2.54 = cm; pounds ÷ 2.2046 = kg. Do not mix Imperial height with metric weight.
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Step 3 — Multiply height × weight. Product = Height(cm) × Weight(kg). This is the core of the height and weight to BSA formula.
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Step 4 — Divide by 3600. Product ÷ 3600.
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Step 5 — Take the square root. BSA (m²) = √(product / 3600). Round to two decimals for most dosing worksheets.
Prefer the calculate body surface area calculator when you need DuBois or Haycock without hand exponents.
Worked example: BSA from height and weight
Adult case: height 170 cm, weight 70 kg — how to calculate body surface area using height and weight with Mosteller.
| Step | Calculation | Result |
|---|---|---|
| Height × weight | 170 × 70 | 11 900 |
| Divide by 3600 | 11 900 ÷ 3600 | 3.3056 |
| Square root | √3.3056 | 1.82 m² |
The BSA value is 1.82 m². With DuBois on the same inputs the result is about 1.81 m² — close agreement in a typical adult.
Why is BSA used for drug dosing?
Why is BSA used for drug dosing? BSA tracks metabolic size better than weight alone for many agents. Common clinical uses:
- Body surface area for chemotherapy dosing / BSA based drug dosing — many cytotoxics are ordered in mg/m² (body surface area calculation for chemotherapy).
- BSA calculator for cardiac index — cardiac index = cardiac output ÷ BSA (L/min/m²).
- How to calculate pediatric dosage by body surface area — some pediatric regimens are BSA-based; use Haycock or the protocol equation.
- How to calculate body surface area for creatinine clearance — Cockcroft-Gault CrCl itself does not use BSA, but indexed GFR/eGFR is reported per 1.73 m²; absolute GFR can be related as GFR (mL/min) ≈ eGFR × (BSA / 1.73). See how to calculate eGFR and the creatinine clearance calculator.
How to calculate dose based on body surface area: Dose = ordered mg/m² × BSA (m²). Cap or adjust only when the protocol or label says so.
Mosteller vs DuBois BSA formula
Which BSA formula is most accurate? Both are estimates. Use the equation named by the protocol — do not switch between Mosteller and DuBois mid-course for the same patient.
| Feature | Mosteller (1987) | DuBois & DuBois (1916) |
|---|---|---|
| Equation | √[(H×W)/3600] | 0.007184 × H0.725 × W0.425 |
| Simplicity | Square root only — ideal manually | Needs fractional exponents |
| Common use | Bedside, nursing, quick checks | Historical reference; many labels |
| Adult agreement | Usually within a few % of DuBois | Classic comparator |
| Pediatrics | Often acceptable | Less ideal in infants; prefer Haycock |
BSA vs BMI difference
Body surface area vs body mass index answer different questions. BSA estimates surface area for dosing and physiologic indexing; BMI classifies weight relative to height for metabolic risk.
| Feature | BSA | BMI |
|---|---|---|
| What it measures | Estimated surface area (m²) | Weight / height² (kg/m²) |
| Typical use | Chemo mg/m², cardiac index, some pediatric doses | Adiposity / obesity categories |
| Inputs | Height + weight (formula-specific) | Height + weight only |
| Interchangeable? | No — not a BMI substitute | No — not a BSA substitute |
Compare with our BMI calculator when you need adiposity categories, not surface area.
How to calculate body surface area in adults & nursing
For how to calculate body surface area in adults, Mosteller or DuBois with accurate standing height and dry weight is standard. For how to calculate body surface area nursing: confirm units, use the protocol equation, document BSA to two decimals, and recheck before locking a how to calculate body surface area for medication doses worksheet. How to calculate total body surface area in this dosing sense means total estimated BSA in m² from height and weight — not burn-chart percentages (out of scope here).
BSA FAQ
What is the body surface area formula?
What is body surface area formula / body surface area formula explained: Mosteller: BSA (m²) = √[(cm × kg) / 3600]. DuBois: 0.007184 × cm0.725 × kg0.425. Haycock: 0.024265 × cm0.3964 × kg0.5378.
What formula do doctors use for BSA?
Most often Mosteller at the bedside; DuBois when a label cites it; Haycock in many pediatric settings. Match the named equation in the protocol.
Is Mosteller or DuBois more accurate?
Both estimate BSA. Adult results usually agree closely. Accuracy depends more on correct height/weight and consistent equation choice than on picking one “winner.”
What is a normal BSA value?
Many adults fall near 1.6–2.0 m². The classic “average” indexing value used with eGFR is 1.73 m². Individual BSA varies with stature and weight.
How accurate is BSA calculation?
Height–weight formulas are validated estimates, not direct measurements. Extreme habitus, fluid overload, and unit errors reduce accuracy. Verify inputs before chemotherapy or other high-risk BSA dosing.
Why is BSA used for drug dosing?
BSA correlates with blood volume and clearance better than weight alone for many agents, so chemo and some pediatric doses are ordered per m². Cardiac index also indexes to BSA.
What is the BSA vs BMI difference?
BSA is surface area (m²) for dosing/indexing. BMI is kg/m² for adiposity categories. They are not interchangeable.
How do you calculate body surface area in m²?
Use cm and kg in Mosteller: √[(H × W) / 3600]. Example: 170 cm, 70 kg → 1.82 m². Or use the BSA calculator.
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