What is BSA? What does body surface area mean?
BSA — body surface area — estimates the external surface of the human body in square meters (m²). A body surface area calculator turns height and weight into that number so you can calculate my body surface area, scale medication doses, or relate kidney results to the classic 1.73 m² reference.
Why calculate body surface area?
Direct measurement of total body surface area is impractical, so clinicians use a formula to calculate body surface area from height and weight. BSA tracks metabolic mass better than weight alone for many drugs — which is why oncology BSA calculator workflows, methotrexate dosing, and other dose calculation based on body surface area still start here.
BSA also bridges renal dosing and staging tools on this site: use it with the eGFR calculator when you need a GFR adjusted for body surface area (de-index with BSA ÷ 1.73), with the creatinine clearance calculator for Cockcroft–Gault drug labels, and with electrolyte tools such as the corrected calcium calculator, anion gap calculator, and free water deficit calculator when the same admission needs both dosing and acid–base workups.
How height + weight become BSA (m²)
Every major body surface area calculation method uses the same two inputs.
Average human body surface area
Typical BSA values (m²) used as teaching anchors — not diagnostic cut-offs.
BSA m² meaning: 1.73 m² is the GFR indexing reference for an “average” adult.
Body surface area formula (calculation methods)
There is no single universal equation. This total body surface area calculator implements the methods clinicians actually compare — including the ones used by common bedside references (Mosteller, Du Bois, Haycock) so you can see agreement before dosing.
Mosteller RD. N Engl J Med 1987. Ideal when you need a fast calc m² answer at the bedside.
Du Bois & Du Bois, 1916. Still named in many adult and chemotherapy protocols.
| Method | Equation (W kg, H cm) | Best known for |
|---|---|---|
| Haycock | 0.024265 × W0.5378 × H0.3964 | Pediatric BSA / infants–adults |
| Gehan & George | 0.0235 × W0.51456 × H0.42246 | Chemotherapy literature |
| Fujimoto | 0.008883 × W0.444 × H0.663 | Japanese anthropometry |
| Boyd | 0.03330 × W(0.6157−0.0188·log₁₀W) × H0.3 | Growth / historic pediatric work |
| Schlich | Sex-specific exponents (3-D scan) | Male vs female surfaces |
| Takahira | 0.007241 × W0.425 × H0.725 | Du Bois–style Asian coefficients |
How to calculate body surface area using height and weight
- Collect inputs. Weight (kg or lb) and height (cm or ft+in).
- Convert units. Formulas expect kg and cm. lb ÷ 2.2046 → kg; inches × 2.54 → cm.
- Pick the equation. Mosteller for speed; Du Bois when a label cites it; Haycock for pediatric body surface area.
- Compute BSA in m². That is how to calculate body surface area in square meters — the unit used for mg/m² dosing and eGFR indexing.
- Optional dose. Multiply BSA by the ordered mg/m² to get milligrams.
Worked example: calculate body surface area
Adult: 70 kg · 170 cm · Mosteller
- Product:
170 × 70 = 11,900 - Divide:
11,900 ÷ 3600 = 3.3056 - Square root:
√3.3056 ≈ 1.818 m²
Pediatric BSA calculator (children, infant, neonate)
Searching how to calculate body surface area in pediatrics or body surface area calculator child usually means the same height–weight math with extra care: measure length accurately in infants, prefer Haycock or Mosteller, and never invent a dose outside a pediatric formulary. A body surface area calculator neonate result near 0.2–0.3 m² is expected — tiny absolute errors still move mg/m² doses a lot.
BSA dosing calculator for medication & chemotherapy
Body surface area formula for dose calculation: Dose (mg) = Target mg/m² × BSA (m²). Multiply your protocol’s mg/m² target by the BSA result above — this is an educational body surface area calculator for medication doses / body surface area calculator for chemotherapy. Narrow therapeutic-index drugs (many cytotoxics, high-dose methotrexate) need protocol caps, AUC rules, and pharmacist verification — BSA alone is not enough.
Carboplatin note: Calvert AUC dosing uses GFR (often via creatinine clearance), not plain mg/m² × BSA. Use our creatinine clearance calculator and institutional oncology guidance together.
BSA, eGFR and creatinine clearance
Labs report eGFR in mL/min/1.73 m². To approximate non-indexed filtration: mL/min ≈ eGFR × (BSA ÷ 1.73). Run height and weight here, then open the eGFR calculator for CKD-EPI staging and the creatinine clearance calculator when a label still demands Cockcroft–Gault mL/min. For AKI context alongside dosing, pair with the FeNa calculator or BUN:creatinine ratio calculator. Step-by-step CrCl math is also covered in our how to calculate creatinine clearance guide.
FAQ
Whats BSA / what does body surface area mean?
BSA estimates external body surface in m² from height and weight. It is used for mg/m² dosing, cardiac index, and as the 1.73 m² reference for indexed eGFR.
How is body surface area calculated?
Convert to kg and cm, then apply a published equation such as Mosteller √((H×W)/3600) or Du Bois 0.007184×W⁰·⁴²⁵×H⁰·⁷²⁵. This calculator runs several methods side by side.
How do you calculate body surface area for a child?
Use accurate height/length and weight, then Mosteller or Haycock. Treat neonate and infant results carefully — small input errors change doses.
How to calculate body surface area in m² / square meters?
All standard clinical formulas already output m². Convert ft² by multiplying m² × 10.764 if needed.
Is this the same as MDCalc, Medscape, GlobalRPH or NHS BSA tools?
Those references use the same published equations. Results match when inputs, units and the chosen formula match. Always follow your local formulary if it names a specific method.
What about nomograms for calculating body surface area?
Paper nomograms estimate BSA from height–weight charts. Digital calculators replace them with the underlying equations — usually more precise than reading a printed grid.
Adjusted body surface area calculator — when does BSA fail?
Extremes of obesity, amputation, severe edema, or burns can make height–weight BSA misleading. Use clinical judgment and protocol-specific alternatives.
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User Reviews
4.8 / 5 from 3 recent users of this calculator
Mosteller and Du Bois side-by-side is exactly what we need before locking a chemo mg/m² dose. Clean on mobile too.
Haycock option for pediatrics is clear, and the 1.73 m² comparison helps when we de-index eGFR.
Fast BSA from cm/kg with a clear Calculate button. Always verify against protocol caps.