Body Surface Area Calculator — Mosteller, Du Bois and Haycock

Enter height and weight once to calculate body surface area (BSA) with three established formulas and compare their estimates in square metres.

Formula review: July 30, 2026. Calculations run only in your browser; entered measurements are not sent to Starlight Tools.

Height and weight

Unit system

Metric (cm, kg) US (ft/in, lb)

Height (cm) Accepted range: 20–300 cm.

Weight (kg) Accepted range: 0.2–700 kg.

Private by design: the calculator does not store or transmit height, weight, or results. Copy and download actions happen locally.

BSA comparison

Mosteller estimate

— m²

Enter height and weight to compare the three formulas.

Mosteller Square-root formula

— m² Comparison baseline

Du Bois & Du Bois Height/weight power equation

— m² —

Haycock Validated from premature infants to adults

— m² —

Formula spread

The range across methods will appear here.

Converted metric inputs: —

Medical safety and limits

This calculator estimates BSA; it does not prescribe a dose. Never start, stop, or change a medicine using this page alone. Medication instructions may specify a particular BSA equation, rounded or unrounded values, dose caps, current measured weight, organ-function adjustments, and independent verification by a clinician or pharmacist.

For treatment, monitoring, cardiac indexing, burns, or paediatric care, use the method and safeguards required by the relevant professional protocol. If a result appears inconsistent with a clinical record, ask the treating team to confirm the measurements, formula, rounding, and units.

BSA formulas used

Each equation returns body surface area in square metres (m²), using height H in centimetres and weight W in kilograms. US inputs are converted before calculation: 1 inch = 2.54 cm and 1 lb = 0.45359237 kg.

Mosteller

BSA = √((H × W) / 3600)

Published by R. D. Mosteller in 1987 as a simplified BSA calculation.

Du Bois & Du Bois

BSA = 0.007184 × H^0.725 × W^0.425

The historic 1916 equation was derived from direct surface measurements in a small sample.

Haycock

BSA = 0.024265 × H^0.3964 × W^0.5378

Derived from 81 subjects and validated across premature infants, children, and adults.

Worked BSA examples

Adult example: 175 cm and 70 kg

Mosteller: √((175 × 70) / 3600) = 1.8447 m².

Du Bois: about 1.8481 m². Haycock: about 1.8468 m².

Child-sized example: 100 cm and 15 kg

Mosteller: √((100 × 15) / 3600) = 0.6455 m².

Because equations were derived differently, the comparison can be more noticeable at smaller body sizes.

How to interpret a BSA result

BSA is a body-size estimate, not a health score and not a measure of body fat. A larger or smaller number is not inherently good or bad. The meaningful question is how a specified clinical or research method uses that value.

Result element	What it means	What to check
BSA in m²	Estimated external body surface area.	Current height, current weight, and correct units.
Formula difference	Variation caused by the equations' different constants and exponents.	Which formula the relevant protocol explicitly requires.
Rounded display	This page shows BSA to four decimal places and percent differences to two.	Use the protocol's rounding rules; do not infer a dose from the displayed precision.

Mosteller is widely used because it is easy to calculate. Du Bois remains historically influential but came from a very small original sample. Haycock's study included a broader size range, including infants and children. No single estimate replaces direct clinical judgment or protocol-specific requirements.

Body surface area calculator FAQ

What is body surface area?

Body surface area, or BSA, is an estimate of the body's total external surface, expressed in square metres. These equations estimate it from height and weight rather than directly measuring skin area.

Which BSA formula should I use?

Use the formula named by the applicable clinical protocol, medicine label, research method, or healthcare professional. Mosteller, Du Bois, and Haycock are established formulas, but they are not interchangeable when a method is specified.

Why do the Mosteller, Du Bois, and Haycock results differ?

They use different constants and exponents and were derived from different study populations. The estimates are often close for average-sized adults, but differences can increase at body-size extremes and in infants or children.

Can this calculator be used for medication dosing?

Not by itself. Do not choose or change a dose from this page. BSA-based dosing can depend on a specified formula, current measurements, dose caps, organ function, treatment protocol, and clinician or pharmacist verification.

Can the BSA formulas be used for children?

The equations can calculate a result from a child's current height and weight. Haycock was validated in infants, children, and adults. Any clinical use in a child must follow the equation, dose rules, and safety checks required by the treating team or protocol.

What units does a BSA result use?

The result is in square metres (m²). If you enter feet, inches, and pounds, the calculator converts them to centimetres and kilograms before applying each formula.

Does BSA directly measure skin area?

No. Formula-based BSA is an estimate. Direct measurement methods and newer three-dimensional body scanning can produce different values.

Sources and method review

This page implements the published equations without adding age, sex, diagnosis, or body-composition adjustments. Calculations use full-precision JavaScript numbers and display results rounded to four decimal places.

Mosteller RD. Simplified calculation of body-surface area. New England Journal of Medicine. 1987.
Haycock GB, Schwartz GJ, Wisotsky DH. Geometric method for measuring body surface area: a height-weight formula validated in infants, children, and adults. Journal of Pediatrics. 1978.
NCBI Bookshelf. Body Surface Area, including the Du Bois, Mosteller, and Haycock equations and clinical context.
Formula and content review date: July 30, 2026.

Disclaimer: For general education and arithmetic checking only. This page does not diagnose a condition, assess treatment suitability, or provide medical or medication advice.