BSA Calculator: Body Surface Area Calculator
BSA Calculator: Estimate Body Surface Area with Mosteller and Du Bois Formulas
A BSA calculator estimates body surface area from height and weight. This page lets you calculate an educational estimate in square metres, compare the Mosteller and Du Bois equations, check conversions, and explore how BSA differs from BMI. It is designed for students, educators, researchers, clinicians reviewing the mathematics, and readers who want to understand the concept.
BSA Calculator
Calculate estimated body surface area using standard BSA formulas. Height and weight are required for the standard equations. Calculations run in this browser and are not sent to an external server.
Enter a positive value in the selected format.
Use a current measured value when this is for coursework review.
The two Du Bois labels use the same historical Du Bois and Du Bois equation.
Next step: After entering height and weight, select the dark-blue Calculate BSA button.
Enter height and weight, then select Calculate BSA. The result will include the converted units, selected formula, and a calculation trace.
Mosteller and Du Bois comparison will appear after a valid calculation.
How to read the result
The calculator reports BSA in m², the conventional unit for this estimate, and also shows the equivalent in cm² when useful. The conversion is straightforward: 1 m² equals 10,000 cm². A displayed result such as 1.82 m² is rounded for readability; the unrounded value is retained internally for the comparison and chart calculations.
The selected formula is always named beside the result. That matters because two valid equations can produce slightly different estimates from the same inputs. A difference is not automatically an error. It reflects the formula’s mathematical structure, the reference population used when it was developed, and the fact that estimated BSA is not a direct scan of a person’s actual outer surface.
What Is Body Surface Area?
Body surface area, commonly abbreviated as BSA, is an estimated measure of the external area of the body. It is expressed in square metres and is calculated from variables such as height and weight. The concept began as an attempt to relate body size to physiological processes; over time, many equations have been proposed. The Du Bois and Du Bois equation and the later simplified Mosteller equation are two of the best-known examples.[1] [2]
BSA is not the same thing as visible skin area measured with a scanner, and it is not a complete description of body composition. It is a mathematical proxy. In clinical science, proxies are useful when their assumptions are understood and when the result is used with the other information relevant to the question being asked.
Depending on the setting, BSA may be used as one input for indexing physiological measurements, describing the extent of a burn or skin involvement, standardizing research measurements, or expressing selected medication prescriptions. Its purpose is context-specific. The same BSA number can be appropriate for a classroom calculation but insufficient for a real clinical decision.
Why are height and weight required?
Standard BSA formulas combine height and weight because people with the same weight can have different heights and proportions, while people with the same height can have different weights. Height-only and weight-only shortcuts discard information that the standard equations were designed to use. For this reason, a trustworthy body surface calculator should ask for both variables rather than pretending that weight alone uniquely determines BSA.
Accurate inputs still do not make the output exact. A scale may be affected by clothing, fluid retention, equipment calibration, or timing. Height may be measured with posture or equipment differences. Small changes in either input can change the estimate, especially when results are rounded early.
Mosteller Formula and Du Bois Formula
The calculator uses two widely recognized formulas. Mosteller is popular in teaching and routine calculation because the expression is comparatively simple. The Du Bois and Du Bois formula is an established historical equation that uses exponents for height and weight. Neither label means that one formula is universally superior in every person, age group, or clinical application.[2]
Mosteller BSA formula
To use Mosteller, convert height to centimetres and weight to kilograms first. Multiply the two converted values, divide by 3,600, and take the square root. The calculation is dimensionally organized so that the final conventional expression is reported in square metres.
Du Bois and Du Bois formula
The Du Bois formula uses fractional powers rather than a square root. It is often encountered in older references, clinical calculators, and historical studies. It remains important to recognize the equation, but a reader should not assume that a historical formula is automatically the correct choice for every modern use case.
Why might results differ?
Equations encode different assumptions. They were derived using different approaches, samples, and mathematical fits. A small difference may be expected; a large difference can signal a unit error, an input error, or a situation in which the formulas behave differently. The safest workflow is to name the equation, preserve the converted inputs, and follow the standard selected by the relevant course, institution, research protocol, or clinician.
| Feature | Mosteller | Du Bois |
|---|---|---|
| Inputs | Height in cm and weight in kg | Height in cm and weight in kg |
| Main equation | √[(height × weight) ÷ 3600] | 0.007184 × height^0.725 × weight^0.425 |
| Practical character | Compact and easy to reproduce by hand | Historical power-law equation |
| Interpretation | Estimated BSA, not a direct measurement | Estimated BSA, not a direct measurement |
| Best practice | Use consistently and document the formula | Use consistently and document the formula |
Unit Conversion for BSA Calculations
Many calculation errors happen before the formula is used. The Mosteller and Du Bois equations in this article expect centimetres and kilograms. The interface accepts metres, feet and inches, pounds, or kilograms and converts internally without changing what the user entered on screen.
| Conversion | Relationship | Why it matters |
|---|---|---|
| Metres to centimetres | 1 m = 100 cm | Mosteller and Du Bois use height in cm. |
| Feet and inches to centimetres | 1 inch = 2.54 cm; total inches = feet × 12 + inches | Height must be one continuous centimetre value. |
| Pounds to kilograms | 1 kg ≈ 2.20462 lb; kg = lb ÷ 2.20462 | The formulas use mass in kg. |
| Square metres to square centimetres | 1 m² = 10,000 cm² | Area units are squared, so the factor is 100². |
Rounding during conversion can create avoidable differences. For a careful classroom calculation, keep several decimal places internally and round the final BSA to the precision requested by the exercise. In clinical work, follow the rounding convention specified by the institution or protocol. This calculator displays two decimal places by default but can show one or three.
BMI and BSA Are Different Measurements
BMI and BSA both use height and weight, but they answer different mathematical and practical questions. BMI is weight in kilograms divided by height in metres squared. The Centers for Disease Control and Prevention describes adult BMI as a screening measure that should be considered alongside other factors, not as a complete health assessment.[3] BSA is an estimated area in square metres and is used in different contexts.
| Measurement | Equation | Typical unit | What it does not tell you by itself |
|---|---|---|---|
| BMI | Weight(kg) ÷ Height(m)² | kg/m² | It does not diagnose health or uniquely determine body surface area. |
| BSA | Mosteller or another named BSA equation | m² | It does not determine a safe medicine dose or describe every aspect of body composition. |
BMI cannot replace BSA. Even when BMI and height are known, the weight used to derive BSA must first be calculated. If only BMI is supplied, there are infinitely many height-and-weight pairs that can share that BMI, so a unique BSA cannot be recovered. This is why the BSA-from-BMI tool below requires height as well as BMI.
Additional BSA Calculation Tools
The following tools use the same unit discipline as the main calculator. They are separated so that a learner can inspect one calculation at a time. Each result is an estimate or a mathematical relationship and should be documented with its inputs and formula.
BMI and BSA Calculator
Calculate BMI and BSA separately from height and weight. BMI is not a substitute for BSA, and neither output is a diagnosis.
Enter height and weight in metric units.
Calculate BSA From BMI
A BMI value alone is insufficient to determine a unique BSA because BMI does not retain height and weight separately. If height and BMI are known, weight can be derived mathematically with Weight(kg) = BMI × Height(m)², after which a standard BSA equation can be used.
Enter a height and BMI to derive a mathematical weight estimate.
BSA Unit Converter
Use this simple converter when an exercise or report requires an area unit other than square metres. This changes units only; it does not recalculate BSA.
Enter an area value.
Pediatric BSA Calculator
This pediatric BSA calculator demonstrates the mechanics of using height and weight with a named equation. It does not assess a child’s condition, growth, hydration, body composition, or treatment plan.
Enter height and weight in centimetres and kilograms.
BSA Calculator for Chemotherapy
In oncology education, BSA may appear as one part of a prescription expressed per square metre. This tool performs arithmetic only. It does not name a drug, supply a regimen, suggest a dose, or apply a dose adjustment.
Enter the dose per square metre exactly as prescribed by the patient’s oncology team or treatment protocol. No default drug dose is provided.
Enter height, weight and the prescribed dose per m².
BSA-Based Dose Calculator
This compact tool multiplies a BSA that you enter by a prescribed dose per square metre that you enter. It does not determine what the prescription should be.
Enter both values to perform the multiplication.
Cardiac Index Calculator with BSA
Cardiac index is a mathematical relationship between cardiac output and BSA. It is shown here for educational review and requires appropriate clinical context; this tool does not diagnose heart disease or interpret a person’s cardiac function.
Enter cardiac output and BSA.
Illustrative BSA Examples
The following worked examples are deliberately hypothetical. They demonstrate technique, not what any individual should do. Every medical example carries the same boundary: Illustrative educational example only. It is not a treatment recommendation.
| Example | Inputs | Method | Estimated result |
|---|---|---|---|
| 1. Adult with Mosteller | 170 cm, 70 kg | √[(170 × 70) ÷ 3600] | About 1.82 m² |
| 2. Adult with Du Bois | 170 cm, 70 kg | 0.007184 × 170^0.725 × 70^0.425 | About 1.81 m² |
| 3. Formula comparison | 170 cm, 70 kg | Compare the unrounded outputs before rounding | Small difference is expected |
| 4. Feet and inches | 5 ft 7 in, 70 kg | (5 × 12 + 7) × 2.54 = 170.18 cm; then Mosteller | About 1.82 m² |
| 5. Pounds | 170 cm, 154.3 lb | 154.3 ÷ 2.20462 ≈ 70 kg; then Mosteller | About 1.82 m² |
| 6. BMI and BSA | 170 cm, 70 kg | BMI = 70 ÷ 1.70²; BSA calculated separately | BMI about 24.2; BSA about 1.82 m² |
| 7. Pediatric arithmetic | 110 cm, 18 kg | Mosteller formula | About 0.74 m² |
| 8. m² to cm² | 1.82 m² | 1.82 × 10,000 | 18,200 cm² |
| 9. User-supplied mathematical dose | BSA 1.82 m²; entered prescription 100 units/m² | 1.82 × 100 | 182 units mathematically; not a treatment recommendation |
| 10. Cardiac index arithmetic | Cardiac output 5 L/min; BSA 1.82 m² | 5 ÷ 1.82 | About 2.75 L/min/m²; interpretation requires clinical context |
Formula Reference and Variable Definitions
| Variable or term | Meaning |
|---|---|
| BSA | Estimated body surface area, conventionally reported in square metres. |
| Height | Body height, converted to centimetres for the BSA equations used here. |
| Weight | Body mass, converted to kilograms for the BSA equations used here. |
| BMI | Body mass index: weight in kg divided by height in metres squared. |
| m² | Square metre, the conventional BSA unit. |
| cm² | Square centimetre; 10,000 cm² equals 1 m². |
| Mosteller formula | Square-root BSA equation using height in cm and weight in kg. |
| Du Bois formula | Historical power-law BSA equation using height in cm and weight in kg. |
| Dose per m² | A prescribed rate expressed per square metre; the tool never supplies this value. |
| Cardiac output | Volume of blood pumped per minute, entered here in L/min. |
| Cardiac index | Cardiac output divided by BSA, reported here in L/min/m². |
Mosteller: BSA = √[(Height(cm) × Weight(kg)) ÷ 3600] Du Bois: BSA = 0.007184 × Height(cm)^0.725 × Weight(kg)^0.425 BMI: BMI = Weight(kg) ÷ Height(m)^2 Cardiac index: CI = Cardiac output ÷ BSA BSA-based arithmetic: mathematical amount = BSA × prescribed amount per m²
Native Canvas Visualizations
The charts on this page are drawn with the browser’s native Canvas API. They are teaching aids rather than validated clinical graphs. The visual displays use labels and text summaries so that essential information is not conveyed by colour alone.
Mosteller versus Du Bois
Run the main calculator to populate the comparison chart.
BSA versus body weight
Run the main calculator to view an educational weight relationship.
BSA versus height
Run the main calculator to view an educational height relationship.
BMI and BSA relationship
Run the BMI and BSA calculator to view the entered pair.
Cardiac output and cardiac index
Run the cardiac index calculator to view the entered pair.
BSA in Nursing Education and Clinical Calculations
Nursing students often encounter BSA as a calculation exercise because it combines measurement, conversion, a named formula, arithmetic order, rounding, and documentation. A sound nursing BSA calculation is not just a number. It is a reproducible record of what was measured, which units were used, which equation was selected, and how the final value was rounded.
A practical learning sequence
- Confirm that height and weight are current, relevant, and measured in a reliable way for the intended exercise or clinical workflow.
- Write the units beside the values. Convert metres or feet and inches to centimetres, and pounds to kilograms.
- Name the equation before substituting values. For example, write “Mosteller” rather than leaving the formula implicit.
- Keep enough precision through the intermediate steps. Do not round the converted weight before multiplying unless your instructions require it.
- Check the order of operations, especially the square root in the Mosteller equation.
- Compare the final result with a second method only when the educational or institutional process calls for that check. A comparison is not permission to choose whichever answer looks more convenient.
- Document the BSA with its unit and the formula used. If the value will enter a medication workflow, use the independent verification process required by the institution.
These habits are more valuable than memorizing a single “normal” BSA value. They help a learner recognize a unit mismatch or implausible result before the number is carried into a more consequential calculation.
Pediatric BSA: Why Extra Context Matters
A pediatric BSA calculator can demonstrate the arithmetic, but children are not simply small adults. Age, growth pattern, body proportions, hydration, illness, measurement quality, indication, and the medicine or protocol involved can all affect the clinical meaning of a calculation. The NCBI review of BSA formulas notes that different equations may behave differently in children and that formula selection should account for the intended population and context.[2]
For education, the Mosteller equation is easy to inspect and may be used as a teaching example. In practice, the governing institution or protocol may specify another validated method. A pediatric medication dose also may depend on factors beyond BSA, and the person responsible for the order must verify the full clinical picture. This page therefore avoids pediatric dose recommendations and does not classify a child’s BSA as normal or abnormal.
Pediatric BSA calculations are educational estimates. Pediatric medication dosing must follow the child’s clinical condition, age, weight, medication-specific guidance and the treating clinician’s instructions.
If a child’s height or weight is uncertain, do not “repair” the data by guessing inside a calculator. Repeat the measurement or use the method required by the responsible clinical team. If the exercise is academic, state the assumption clearly in the written work.
BSA for Chemotherapy and Oncology Calculations
Searches for “BSA calculator chemo” or “BSA calculator for chemotherapy” often reflect an important but potentially dangerous misunderstanding: calculating BSA is not the same as determining a chemotherapy dose. Some oncology prescriptions are expressed per square metre, but the prescription and the protocol come from qualified professionals and include checks that an online calculator cannot perform. The broader clinical literature describes BSA-based dosing as a subject with known variability and ongoing debate, rather than a universal rule that automatically makes a dose safe.[2]
The safe mathematical relationship is simple:
That equation becomes a treatment calculation only inside an authorized workflow. A responsible sequence is to calculate or confirm BSA; obtain the prescribed dose per square metre from the applicable treatment protocol; multiply the values; apply only the adjustments authorized by the responsible clinician and protocol; and complete the required independent verification. This article deliberately does not supply drug names, regimens, dose caps, concentration recommendations, or adjustment rules.
The oncology tool on this page therefore requires the user to enter the prescribed amount per square metre. It contains no default dose. Its result is labelled “mathematical calculation only — not a treatment recommendation.” If a result is being considered for actual care, stop and use the official clinical process instead of relying on this page.
Cancer treatment can affect healthy tissues and side effects can vary from person to person, even among people receiving the same type of treatment.[4] That is one reason a calculator cannot replace review of laboratory findings, treatment history, organ function, allergies, current medicines, performance status, and the protocol-specific instructions of the oncology team.
Body Surface Area Using Weight Only
The phrase “body surface area formula using weight only” is common in search queries, but standard Mosteller and Du Bois calculations require both height and weight. Weight-only estimates may exist in specialized settings or population-specific research, but they are not interchangeable with the standard equations used on this page. A calculator that silently turns weight into BSA without stating a validated method would create false precision.
If height is unavailable, the correct educational answer is that the standard calculation cannot be completed. Record the missing variable rather than inventing it. If a clinical service has authorized an alternative method, follow that service’s documented method and do not assume that a general internet calculator implements it.
BSA from BMI: What Can and Cannot Be Inferred
BMI alone cannot uniquely determine BSA. To see why, take a BMI value of 24.2. A person who is 1.70 m tall would have a mathematical weight of 24.2 × 1.70², or about 69.9 kg. A person with the same BMI at 1.50 m would have a different mathematical weight of about 54.5 kg. Because the height and weight pairs are different, the BSA estimates are also different.
When both BMI and height are known, the relationship is:
The BSA-from-BMI calculator uses this derivation transparently and labels the result as a mathematical estimate. It is not a way to avoid measuring weight in a real clinical setting. A derived weight can inherit the limitations of the BMI input and the height input, and it should not be treated as a measured value.
When BSA Is Used: Context, Not Automatic Meaning
BSA has applications in pharmacology, physiology, research, and some specialized clinical measurements. The NCBI overview describes uses that include indexing cardiac output to obtain cardiac index, standardizing research observations, and supporting selected pharmacological calculations.[2] These uses do not make BSA a universal measure of health, and they do not remove the need for context.
Cardiac index
Cardiac index is calculated as cardiac output divided by BSA:
The quotient is a mathematical result. Its interpretation depends on how cardiac output was measured, the patient’s clinical state, the measurement conditions, and the professional reference framework. This article’s cardiac index module therefore reports units and arithmetic but does not diagnose heart disease or label a value as safe, unsafe, normal, or abnormal.
Research and indexing
Researchers may use BSA to make certain measurements more comparable across people of different sizes. However, the formula should be named in a methods section because formula choice can change the indexed result. Reproducibility depends on preserving the inputs, units, equation, rounding convention, and any protocol-specific definition of the variable.
Burns and surface involvement
Clinical burn assessment may use specialized charts and clinical examination to estimate the percentage of total body surface area affected. That purpose is different from estimating a person’s overall BSA from height and weight. This general-purpose calculator is not a burn-assessment tool and should not be used to guide fluid resuscitation or emergency treatment.
Limitations of BSA Calculations
A BSA calculation is useful when the question, equation, inputs, and clinical workflow are aligned. It is limited when any of those pieces are unclear. The following limitations are especially important for learners and readers who encounter BSA in medication or research contexts.
- It is an estimate. Formula-derived BSA is not a direct measurement of the actual skin surface.
- Equations differ. Mosteller and Du Bois can produce different estimates, and the difference may be more consequential when a result is multiplied by another quantity.
- Input errors propagate. A wrong height, wrong weight, incorrect unit, or poor measurement can change the output.
- Body composition matters. People with unusual proportions, obesity, oedema, fluid shifts, amputation, or other circumstances may not be well represented by a simple height-weight equation.
- Age group matters. Infants, children, and adolescents may have proportions and clinical considerations that differ from adult reference populations.
- Rounding matters. Rounding before the final step can create an avoidable discrepancy.
- BSA is not a universal dosing rule. Clinical protocols may use weight, renal function, organ function, pharmacokinetic information, maximum doses, dose intensity, or other parameters.
- Online tools have boundaries. A browser calculator cannot see the patient, validate the prescription, inspect a medication label, or know local policy.
These limitations do not make BSA useless. They define how it should be used: transparently, consistently, and as one input within a wider process.
Common BSA Calculation Mistakes
| Mistake | Why it causes trouble | Better habit |
|---|---|---|
| Mixing pounds and kilograms | The formula receives a mass value in the wrong scale. | Convert lb to kg before substitution. |
| Mixing metres and centimetres | A factor of 100 is introduced into the height term. | Convert height to cm for the listed equations. |
| Forgetting the square root | Mosteller’s intermediate product is mistaken for BSA. | Apply the square-root operation after division. |
| Using BMI as BSA | The units and meanings are different. | Calculate BMI and BSA independently. |
| Using BMI alone to infer BSA | BMI does not uniquely preserve height and weight. | Require height and derive weight only when mathematically appropriate. |
| Rounding too early | Small conversion errors can compound. | Keep precision internally and round at the end. |
| Choosing a dose from a calculator | A numerical output is mistaken for a prescription. | Enter only an authorized prescribed value and verify clinically. |
| Ignoring institutional procedure | The local formula or independent check may differ. | Follow the governing policy and document the method. |
Best Practices for a Transparent BSA Calculation
Before accepting a result, verify the height and weight, confirm the units, state the equation, preserve precision, and inspect the output for an input error. If the number will be used in a clinical environment, compare it with the official system or institution-approved calculator and complete the required independent review. The aim is not to force two formulas to agree. The aim is to make the calculation reproducible and to surface discrepancies early.
For learning, write the calculation in a way another person can audit. For research, include the formula and rounding convention in the methods. For clinical work, use the institution’s approved process and do not transfer a result into a prescription workflow without the required verification. For personal education, avoid entering names, medical record numbers, addresses, or other unnecessary identifying information.
Frequently Asked Questions About BSA
1. What is a BSA calculator?
A BSA calculator estimates body surface area from height and weight using a named equation such as Mosteller or Du Bois. It is a mathematical and educational tool, not a diagnostic system or an automatic medication-dose selector.
2. What is body surface area?
Body surface area is an estimated external area expressed in square metres. It is calculated from body-size inputs and is used in selected clinical, research, and physiological contexts. It is not a direct scan of actual skin surface and should not be interpreted alone.
3. How is BSA calculated?
Most standard equations use height and weight. The Mosteller equation is BSA = √[(height in cm × weight in kg) ÷ 3600]. The Du Bois equation is BSA = 0.007184 × height(cm)^0.725 × weight(kg)^0.425. Both produce estimates.
4. What is the Mosteller formula?
The Mosteller formula is a simplified BSA equation: BSA in m² equals the square root of height in centimetres multiplied by weight in kilograms, divided by 3,600. It is easy to reproduce by hand and was published by R. D. Mosteller in 1987.[1]
5. What is the Du Bois formula?
The Du Bois and Du Bois formula is an historical power-law equation: 0.007184 × height in cm raised to 0.725 × weight in kg raised to 0.425. It remains a commonly encountered reference equation, but no formula is universally preferred in every context.[2]
6. Which BSA formula is commonly used?
Mosteller is commonly taught because its arithmetic is compact, while Du Bois is frequently seen in historical references and medical calculators. The appropriate choice depends on the course, institution, study, or protocol. The important practice is to name and use the selected formula consistently.
7. What is the BSA formula in square metres?
For Mosteller, BSA(m²) = √[(Height(cm) × Weight(kg)) ÷ 3600]. For Du Bois, BSA(m²) = 0.007184 × Height(cm)^0.725 × Weight(kg)^0.425. Height and weight must be in the units specified by the equation.
8. How do I calculate BSA from height and weight?
Convert height to centimetres and weight to kilograms, choose the named equation, substitute the values, keep precision through the intermediate steps, and round the final answer as directed. The main calculator automates these conversions and shows the calculation trace.
9. Can BSA be calculated from weight only?
Not with the standard Mosteller or Du Bois equations used here. They require both height and weight. Weight-only estimates may exist in specialized situations, but a general calculator should not pretend that weight alone uniquely determines standard BSA.
10. Can I calculate BSA from BMI?
BMI alone is not enough. If height is also known, weight can be derived mathematically as BMI × height in metres squared, and that derived weight can be used in a BSA equation. The result inherits the assumptions of the BMI and height inputs.
11. What is the difference between BMI and BSA?
BMI is weight in kilograms divided by height in metres squared and is generally used as a screening measure. BSA is an estimated body area in square metres. They have different equations, units, and purposes; BMI cannot replace BSA.[3]
12. What is a BSA calculator for chemotherapy?
It is a tool that can calculate BSA when a protocol uses BSA as one parameter. It cannot determine a chemotherapy regimen or decide a safe dose. This page’s oncology module multiplies BSA only by a dose-per-square-metre value explicitly entered by the user and labels the result as arithmetic.
13. How is BSA used in medication calculations?
Some prescriptions may be expressed per square metre, but BSA is only one possible parameter in a medication workflow. The final order also depends on the prescription, indication, protocol, patient-specific findings, formulation, units, and independent verification. Never select a dose from BSA alone.
14. Is BSA used for chemotherapy dosing?
BSA-based expressions can appear in oncology, but the existence of a BSA formula does not make an online result a treatment recommendation. Actual dosing must follow the applicable protocol and the oncology team’s instructions, including all required checks and adjustments.[2] [4]
15. Can this calculator determine my chemotherapy dose?
No. It can perform a mathematical multiplication only when you enter a prescribed dose per m². It does not recommend a drug, regimen, dose, concentration, adjustment, or administration instruction. Ask the treating oncology team or pharmacist to verify any real order.
16. What is BSA dosing?
BSA dosing is a shorthand for expressing a prescribed amount in relation to square metres of estimated body surface area. The phrase describes a mathematical format, not a universal safety rule. The prescribing professional and protocol determine how it is applied.
17. How do nurses calculate BSA?
Nurses learn to verify measurements, convert units, select the required formula, calculate in the correct order, document the BSA and formula, and complete the institution’s independent medication-calculation checks. An online calculator may support learning but does not replace institutional procedures.
18. What is a pediatric BSA calculator?
It is a calculator that estimates a child’s BSA from height and weight. Pediatric interpretation requires special caution because age, body proportions, illness, growth, medication-specific guidance, and protocol can matter. It must not be used to choose a child’s medication dose.
19. Why do Mosteller and Du Bois give different results?
They are different equations with different mathematical structures and historical derivations. Small differences can be expected. A substantial discrepancy should prompt a review of units, inputs, formula selection, and the context in which the result is being used.
20. What units are used for BSA?
BSA is conventionally reported in square metres, written m². The equivalent square-centimetre value can be calculated by multiplying m² by 10,000. Height and weight are usually converted to centimetres and kilograms for the equations on this page.
21. What is a normal BSA?
There is no single “normal BSA” value that can be applied without context. BSA varies with height, weight, age, body proportions, and the formula used. The calculator intentionally reports the estimate without labelling it normal or abnormal.
22. Can BSA be used to calculate cardiac index?
Yes, cardiac index is mathematically calculated as cardiac output divided by BSA, with units of L/min/m². The result requires clinical context and appropriate measurement methods. This tool does not diagnose heart disease or interpret the number.
23. Can I use this calculator for medical treatment?
No. Use it for education, coursework review, or transparent arithmetic review within an authorized workflow. Do not use it to diagnose, select, change, prepare, or administer medication or chemotherapy.
24. Is this calculator a substitute for professional medical advice?
No. It cannot examine a person, validate a prescription, review laboratory data, or know the applicable institutional protocol. A qualified healthcare professional should confirm anything consequential.
25. How accurate is a BSA calculator?
It can be arithmetically accurate for the values and equation entered, but the clinical estimate remains limited by measurement quality, formula choice, body composition, age, rounding, and context. “Accurate arithmetic” does not mean “complete clinical assessment.”
Privacy, Local Storage, and Accessibility
The calculations in this post run locally in the browser. The page does not require an external API, and the JavaScript does not transmit the entered values to a server. Optional local storage remembers calculator inputs in the same browser so that a learner can return to an unfinished exercise. The Clear Saved Data button removes those saved values.
Do not enter names, medical record numbers, addresses, dates of birth, or other unnecessary personally identifiable health information. Browser storage is not a substitute for an approved clinical information system, and users should follow the privacy and security rules that apply to their setting.
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References
[1] Mosteller RD. “Simplified calculation of body-surface area.” New England Journal of Medicine. 1987;317(17):1098. PubMed: https://pubmed.ncbi.nlm.nih.gov/3657876/
[2] Flint B, Das J. “Body Surface Area.” StatPearls, NCBI Bookshelf. Formula descriptions, applications, variability, and clinical limitations: https://www.ncbi.nlm.nih.gov/books/NBK559005/
[3] Centers for Disease Control and Prevention. “Adult BMI Categories.” BMI equation and explanation that BMI is a screening measure: https://www.cdc.gov/bmi/adult-calculator/bmi-categories.html
[4] National Cancer Institute. “Side Effects of Cancer Treatment.” General information about variability in treatment side effects and the role of the health-care team: https://www.cancer.gov/about-cancer/treatment/side-effects
Affiliation statement: The calculator is not affiliated with, sponsored by, or endorsed by Medscape or any healthcare organization, hospital, pharmaceutical company, or medical authority.
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