Body Surface Area Calculator

Last formula update: September 27, 2026

Trusted Engineering Tools

Enter height and weight to see your body surface area through five named formulas. Compare the results, check the units, and understand what each estimate can—and cannot—tell you.

Decimal & Rounding Policy

Convert weight to kilograms and height to centimeters before calculating body surface area.
Keep the available numerical precision through conversions and formula evaluation.
Display BSA with up to six decimal places, without unnecessary trailing zeros.
Use the entered BSA value directly when solving for a missing measurement.
Display rounding does not change the underlying results or Excel formulas.

Valid range

Weight: 0.2–500 kg after unit conversion.
Height: 20–280 cm after unit conversion.
Entered BSA: 0.01–5 m² after unit conversion.
For split height, enter both parts; inches must be below 12 and centimeters below 100.
These are calculator input limits, not normal or recommended clinical ranges.

Creators

Brinelle Lumquell

Reviewers:

Cavarine Pexmont

Yeldric Vossbourne

Check our editorial policy

Formula Implementation date:

September 27, 2026

Formula Version:

1.0.0

Changelog:

Version 1.0.0

Initial calculator and formula release.

Need help selecting or validating calculations?

Our engineers are here to help you get it right.

How does a BSA Calculator turn height and weight into an area?

BSA Calculator results estimate external body surface area from height and weight. Enter both measurements and select their units. The main result follows the Du Bois formula and appears in square meters. Four additional results show Fujimoto, Gehan and George, Haycock, and Mosteller. Each equation uses the same measurements but fits them differently, so the outputs can vary. The BSA Calculator also lets you inspect a chosen formula when solving a missing height or weight from a known area and the other measurement.

For Du Bois, BSA = 0.007184 × weight(kg)^0.425 × height(cm)^0.725.
For Mosteller, BSA = √(height(cm) × weight(kg) / 3600).
Check units before you compare values; m² and ft² describe the same area at different scales.
Keep the equation name with any copied result. A reverse-solved measurement is model-implied, not measured.
Use the formula and checks named by your clinical protocol. This tool does not set a medication dose.

At 82 kg and 178 cm, the Du Bois estimate is about 2.001206 m². A different formula gives a different estimate for those same inputs. If the number surprises you, recheck height, weight, units, and equation before using it. For patient-specific decisions, have a qualified professional verify the result.

Assumptions used in this calculator

Weight represents the person’s current measured body mass.
Height represents standing height or a reliably measured body length.
Weight and height describe the same person at the same time.
Input units are converted before an equation is evaluated.
Each equation estimates total external body surface area.
Different equations may produce different estimates for identical measurements.
The selected inverse equation determines the missing measurement.
An inverse result requires one known measurement and one known BSA.
Editing BSA while both measurements exist holds height fixed.
Calculations retain available precision until results are displayed.
Input limits control the calculator, not clinical eligibility.
No result establishes an individual medication dose.
Clinical decisions follow the applicable protocol and professional review.

Results are rounded for display.
Internal calculations use full precision.

Formulas Used in Body Surface Area :

Convert weight to kilograms (W) and height to centimeters (H). Each equation gives estimated BSA (A) in square meters. For inverse calculations, c is the named equation's coefficient, p is its weight exponent, and q is its height exponent.

Du Bois

A = 0.007184 × W^0.425 × H^0.725

Fujimoto

A = 0.008883 × W^0.444 × H^0.663

Gehan and George

A = 0.0235 × W^0.51456 × H^0.42246

Haycock

A = 0.024265 × W^0.5378 × H^0.3964

Mosteller

A = √(W × H3600)

Find weight from a known BSA and height

W = (Ac × H^q)^1/p

Find height from a known BSA and weight

H = (Ac × W^p)^1/q

Variables & Definitions

View a complete list of all variables used in this calculator, including definitions and units

Body Surface Area Formula Variables

Symbol	Variable	Unit	Role
W	Body weight	kg	Measured input, or a value solved from BSA and height.
H	Body height or length	cm	Measured input, or a value solved from BSA and weight.
A	Estimated body surface area	m²	Formula result, or a known value entered for inverse solving.
c	Equation coefficient	Depends on p and q	Coefficient from the selected named formula.
p	Weight exponent	Dimensionless	Exponent applied to W in the selected formula.
q	Height exponent	Dimensionless	Exponent applied to H in the selected formula.

Unit Conversion Table

Weight Units and Kilogram Equivalents

Unit Group	Unit Name	Symbol	Equivalent in kg	Used For
Popular Units	Kilogram	kg	1 kg	Base weight input
Popular Units	Pound	lb	0.45359237 kg	Imperial weight input
Popular Units	Stone	st	6.35029318 kg	Body weight in stones
Scientific Units	Gram	g	0.001 kg	Small body weights

Height Units and Centimeter Equivalents

Unit Group	Unit Name	Symbol	Equivalent in cm	Used For
Popular Units	Centimeter	cm	1 cm	Base height input
Popular Units	Meter	m	100 cm	Metric height input
Popular Units	Inch	in	2.54 cm	Imperial height input
Popular Units	Foot	ft	30.48 cm	Imperial height input
Popular Units	Feet and inches	ft / in	30.48 cm per ft + 2.54 cm per in	Split imperial height
Popular Units	Meters and centimeters	m / cm	100 cm per m + 1 cm per cm	Split metric height
Scientific Units	Millimeter	mm	0.1 cm	Short measured lengths

Body Surface Area Units and Square Meter Equivalents

Unit Group	Unit Name	Symbol	Equivalent in m²	Used For
Popular Units	Square meter	m²	1 m²	Base BSA result
Popular Units	Square foot	ft²	0.09290304 m²	Imperial BSA display
Scientific Units	Square centimeter	cm²	0.0001 m²	Small area display

Example Calculation

For a person weighing 82 kg and measuring 178 cm, calculate BSA from both measured inputs.

A = 0.007184 × 82^0.425 × 178^0.725 ≈ 2.001206 m²

Du Bois2.001206 m²Fujimoto1.951288 m²Gehan and George2.025594 m²Haycock2.024398 m²Mosteller2.013565 m²

The five estimates use the same weight and height with different published equations.

The calculator retains available precision and rounds only the displayed results.

Use the equation specified by the relevant clinical or research protocol.

Suppose height is 175 cm and the known Du Bois BSA is 1.9 m². Weight is missing.

W = (1.90.007184 × 175^0.725)^1/0.425 ≈ 74.709486 kg

Solved weight74.709486 kgDu Bois1.900000 m²Fujimoto1.851283 m²Gehan and George1.917017 m²Haycock1.912591 m²Mosteller1.905705 m²

The entered BSA and measured height determine weight under the Du Bois equation.

The other BSA figures are recalculated from that solved weight and the known height.

If weight were known instead, the same equation would solve the missing height.

The inferred measurement depends on the selected equation and input accuracy.

Results are rounded for display.
Internal calculations use full precision.

Calculations Disclaimer

Read important information about accuracy, limitations and responsible use of this calculator

Body surface area calculated from height and weight is an estimate, not a direct measurement of skin area. Different published equations can give different results, especially when body proportions differ from the populations used to develop them. Use the equation required by the relevant clinical or research protocol. This calculator does not determine a medication dose or replace assessment and verification by a qualified clinician, particularly for children, extreme body sizes, or medicines with narrow safety margins.

What will the BSA calculator show from height and weight?

BSA Calculator results start with two measurements: height and weight. Enter both, then read the estimated body surface area in square meters. The primary result uses the Du Bois equation. Four other results let you compare Fujimoto, Gehan and George, Haycock, and Mosteller. BSA Calculator outputs are estimates from mathematical models, not direct measurements of skin. A different formula may produce a different number for the same person. That difference matters when a worksheet or protocol names a specific method.

Start with the result you need. Then check the equation and units shown beside it. This keeps a convenient number from becoming an unexplained number. For medical decisions, use the method specified by the responsible care team and protocol.

Why does the result appear in square meters?

BSA describes an area, so its usual unit is the square meter, written m². A value near 2 m² does not mean a person is two meters tall. It is a modeled estimate of external body area. The calculator can also display square feet. Convert the area only after the height and weight inputs are understood. If you compare two results, keep both in the same area unit. Otherwise, a unit change can look like a formula disagreement.

Which values should you enter first?

Use a measured height and a current weight suited to your task. Select the units that match the measurements you have. Height can be entered in centimeters, meters, inches, feet, feet and inches, or meters and centimeters. Weight can use kilograms, pounds, or stone. The tool converts those values before applying its equations. Check the height field closely: 1.78 m and 178 cm describe the same height, but 1.78 cm does not. If one measurement is missing, a forward BSA estimate cannot be calculated.

How does the default Du Bois result work?

The primary number follows a height-and-weight equation. In the expression below, W is weight in kilograms, H is height in centimeters, and BSA is in m².

BSA_{Du Bois} = 0.007184 × W^0.425 × H^0.725

The coefficient belongs to those specific units. Entering pounds directly as W would give a wrong answer. The calculator handles the conversion when you choose pounds. Du Bois is the displayed starting method, not a universal verdict about which equation belongs in every clinical setting.

What do its exponents change?

The powers describe how the estimate changes when height or weight changes. They are part of an empirical model, not a request to multiply the inputs by 0.425 or 0.725. For a fixed height, a higher weight raises the estimated area. For a fixed weight, a taller height also raises it. These changes are not linear. Doubling weight does not simply double the Du Bois result. Keep the original measurements visible when checking an unexpected number.

How do five BSA formulas differ?

Each equation turns the same height and weight into an estimated area. They use different fitted coefficients and powers. The calculator displays all five to make that choice visible. It does not average them into a single clinical answer. Use one named equation consistently when comparing records. A small spread between methods is expected; it is not automatically an input error. A large surprise deserves a review of units, measurements, and formula selection.

Fujimoto: a different fitted curve

The Fujimoto calculation is another height-and-weight model. Its powers and coefficient differ from Du Bois. Use kilograms and centimeters in this expression:

BSA_Fujimoto = 0.008883 × W^0.444 × H^0.663

At some input pairs, Fujimoto gives a visibly lower estimate. That is a property of the equation, not proof that either result measured the person’s actual skin. If a record specifies Fujimoto, compare its result with Fujimoto, using the same input units and precision.

Gehan and George: another comparison

Gehan and George uses a different balance of height and weight. The calculator evaluates:

BSA_{Gehan and George} = 0.0235 × W^0.51456 × H^0.42246

For the same entries, this output can sit above or below another method. Read the formula name with the number. Copying only the area into a spreadsheet hides the modeling choice. That missing label can confuse later comparisons, especially when a different team uses a different equation.

Haycock: a formula validated across ages

Haycock was studied with infants, children, and adults. This broader validation makes its population context useful to know. It does not remove the need to follow a pediatric protocol. With W in kilograms and H in centimeters:

BSA_Haycock = 0.024265 × W^0.5378 × H^0.3964

Measurements in small children can change quickly. Confirm that both measurements belong to the same assessment, then check the method required for the decision.

Mosteller: the square-root shortcut

Mosteller is easy to check by hand. Multiply height in centimeters by weight in kilograms. Divide by 3,600, then take the square root:

BSA_Mosteller = √((H × W) / 3600)

For 170 cm and 60 kg, the value is √(10,200/3,600), or about 1.6833 m². The simple steps make this equation a useful independent arithmetic check. They do not make it the required method for every patient or protocol.

Which equation should you use for a clinical task?

Start with the instruction that governs the task. A clinical protocol may specify a BSA equation, a measurement date, or a different dosing rule. Use its requirements and ask the responsible professional when they are unclear. The calculator can help you inspect the arithmetic. It cannot choose a medicine, prescribe an amount, assess organ function, or settle a disagreement in care. A plausible result remains an estimate.

For learning, comparing all five outputs is useful. For a regulated or clinical workflow, the named method and independent checks take priority over convenience.

Why might two estimates disagree?

First, confirm the same person, date, height, and weight. Next, compare the formula labels. Then compare units and rounding. Two calculators can differ because they show different methods or decimal places. They can also use different conversion precision. A more serious mismatch may come from treating 1.75 meters as 1.75 centimeters, or entering pounds in a kilogram field. Trace those causes before deciding that the formula failed.

How do you use the calculator in either direction?

The normal route starts with height and weight and returns five BSA estimates. The reverse route begins with a known BSA and one known measurement. Select the equation attached to that BSA, then solve the other measurement. This is algebra on a model. It does not recover a person’s actual weight or height from an area alone. If the chosen BSA came from another method, a reverse result can mislead.

Solve weight from height and a chosen BSA

Suppose you know height and a Du Bois BSA. Rearrange the Du Bois equation, keeping H in centimeters and BSA in m²:

W = (BSA / (0.007184 × H^0.725))^1/0.425

The answer is an implied weight in kilograms. It depends entirely on the selected equation and the two given values. It should never replace a scale measurement when an actual weight is required.

Solve height from weight and a chosen BSA

The same reasoning can solve height when weight and a Du Bois BSA are given:

H = (BSA / (0.007184 × W^0.425))^1/0.725

This produces an implied height in centimeters. It is a consistency check within Du Bois. It cannot identify someone’s measured height from a BSA value without the accompanying weight and equation. Confirm whether the original BSA was rounded before treating the reverse result as precise.

What do unit changes do to the estimate?

Correct unit conversion changes the displayed numbers, not the person’s size. A weight entered as 82 kg represents about 180.8 lb. The equation still receives the kilogram equivalent. Likewise, 178 cm and about 5 ft 10.08 in describe the same height. Changing an output from m² to ft² changes its numerical scale. It does not change the underlying area. Always keep the unit beside a copied result.

Check height in feet and inches

Feet and inches are easy to misread when written as a decimal. Five feet ten inches is not 5.10 feet. Enter 5 in the feet field and 10 in the inches field. The combined height is 70 inches, or 177.8 cm. If a record supplies a decimal number of feet instead, convert it as a decimal length. A few tenths of an inch can affect the last displayed digits, so preserve the original measurement.

Read surface area in square feet

One square meter equals approximately 10.7639 square feet. Thus, a BSA of 2.0000 m² is about 21.5278 ft². This is an area conversion, not a height conversion. A number near 20 ft² may be entirely consistent with one near 2 m². When entering a known BSA for reverse solving, select its actual area unit first. A factor-of-ten difference here can create a very implausible implied measurement.

Where does BSA help, and where does it stop?

BSA can index a quantity to an estimate of body size. That makes it useful in some clinical formulas and research comparisons. Its role depends on the specific measurement and protocol. It does not directly measure body composition, skin condition, disease severity, or treatment suitability. A larger BSA is not a diagnosis. Use the result to answer the defined calculation question, then apply the separate judgment that question requires.

BSA-indexed quantities need their own protocol

A rate stated per m² needs a BSA value, but that is only one part of the calculation. The protocol may specify a formula, caps, adjustments, timing, and checks. Those rules cannot be inferred from a generic BSA output. Keep the original quantity and units in view. Ask a qualified clinician to verify any patient-specific interpretation, especially for medication dosing or a safety-critical decision.

Children and unusual body shapes need care

Equations are models fitted to studied groups. They can disagree more when body proportions differ from those groups. Infants, rapidly growing children, edema, amputations, and substantial changes in weight deserve careful interpretation. A formula comparison shows mathematical spread; it does not identify which result best represents an individual. Record the chosen method and the clinical reason for it. Use a measured height and weight whenever the task calls for measured inputs.

What input errors change the result most?

The biggest avoidable mistakes often begin before the equation. Check for a missing height, a stale weight, a swapped unit, or a decimal in the wrong place. Confirm that kilograms and centimeters are the equation units even if the interface accepts others. Keep the chosen method beside the copied output. If a result looks surprising, calculate Mosteller by hand as an arithmetic cross-check, then inspect the formula selection. Do not interpret a neat-looking number as proof that the inputs were correct.

Check two complete calculations

Consider a training worksheet with 82 kg and 178 cm. Du Bois gives 0.007184 × 82^0.425 × 178^0.725 ≈ 2.001206 m². The other estimates are Fujimoto 1.951288, Gehan and George 2.025594, Haycock 2.024398, and Mosteller 2.013565 m². All five use the same measurements. Their spread follows from their different equations.

Now take a second worksheet: a Du Bois BSA of 1.9 m² and height of 175 cm. Rearranging Du Bois gives W = (1.9/(0.007184 × 175^0.725))^1/0.425 ≈ 74.709486 kg. Rechecking that implied weight yields 1.900000 m² under Du Bois. The other equations yield Fujimoto 1.851283, Gehan and George 1.917017, Haycock 1.912591, and Mosteller 1.905705 m². These are model checks, not records of actual patients.

How can you keep a useful record?

Save the measured height, weight, units, date, equation name, and displayed BSA together. If you solved a value in reverse, label it as implied rather than measured. Keep enough decimal places to reproduce the computation, but avoid claiming more measurement accuracy than the inputs support. The calculator’s copy, share, and export controls can help preserve a worksheet. Review the saved numbers before sending them onward. For any care decision, the responsible professional should verify the inputs, specified method, and interpretation.

Ready to inspect your own numbers? Enter height and weight in the AxiCalculator BSA Calculator, review the five estimates, and keep the formula name with your result.

Frequently Asked Questions

Can I use my BSA result as a personal health score?

BSA estimates an area from height and weight, so it does not grade fitness, nutrition, illness, or skin health, and two people with similar areas can have very different health needs. Keep the equation name and inputs with the result, then discuss any medical interpretation with the professional responsible for your care; the number becomes useful only when attached to a specific, appropriate task and its separate clinical rules.

Why does my BSA seem unchanged after a small weight change?

The underlying estimate may have changed even when a rounded display still shows the same two-decimal number, because the equations respond gradually to modest input changes. Check the unrounded or higher-precision view if available, confirm the current weight and unit, and avoid treating a tiny numerical shift as a meaningful medical change without a defined clinical threshold, a clear purpose for the comparison, and careful professional interpretation of the clinical context.

Can I use a BSA result from last year?

A past result reflects the height, weight, equation, and date used then, so it may not describe the measurements needed for today’s task, especially when weight has changed. Recheck the required measurement date in the relevant workflow, enter the current measured values when appropriate, and preserve the older result with its original details if you need a fair comparison over time and want to distinguish a true measurement change from a change in method.

What should I send someone who asks for my BSA?

Send the area with its unit, the formula name, and the height and weight values used, since an isolated number cannot reveal a unit mix-up or a different equation choice. Add the measurement date and label any reverse-solved height or weight as an implied value, then let the receiving professional decide whether the information fits the intended clinical or research purpose and whether a fresh measurement and assessment is needed.

How do I check a spreadsheet BSA formula against the calculator?

Set the spreadsheet inputs to kilograms and centimeters, use the exact coefficient and exponents for the chosen method, and compare more digits before display rounding. Test one ordinary input pair and one reverse calculation, then check whether your sheet converts pounds or feet before calculation rather than feeding those values directly into a metric coefficient; a matching label alone does not prove matching arithmetic, especially if conversion or rounding steps differ between systems.

Why does solving backwards amplify a rounded BSA?

The inverse Du Bois equations raise a ratio to a power greater than one, so a rounded BSA can shift the implied height or weight more than the original display suggests. Preserve the known measurement’s precision, identify which formula generated the area, and reinsert the solved value into that same equation; report it as model-implied rather than as a newly measured body dimension, and keep the original area and its precision available.

Can I substitute a different BSA equation in an indexed research dataset?

Changing equations changes the denominator of every per-m² quantity, so it can create an artificial difference even when the underlying measurement is identical. Follow the dataset’s prespecified method, document any alternative computation as a separate sensitivity analysis, and avoid merging records with unknown equations as though they shared a single definition; clinical datasets also need their own governance and review before such derived values support any consequential analysis or decision.