Body Surface Area Calculator
Calculate body surface area (BSA) using the Mosteller, DuBois and Haycock formulas from height and weight.
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How to use this calculator
Body surface area (BSA) is an estimate of body surface in m² from height and weight. Three published equations are calculated: Mosteller (square root of height × weight / 3600), DuBois (0.007184 × W^0.425 × H^0.725) and Haycock (0.024265 × W^0.5378 × H^0.3964, fitted on data that included infants and children). This tool also shows their plain average, which is its own addition.
- 1
Enter weight in kilograms.
- 2
Enter height in centimetres.
- 3
Read the BSA from each of the three published formulas, plus the plain average this tool adds. If a protocol names one formula, look at that line.
Frequently asked questions
Which formulas are calculated?
Three. Mosteller: BSA = √(height in cm × weight in kg / 3600). DuBois: 0.007184 × weight^0.425 × height^0.725. Haycock: 0.024265 × weight^0.5378 × height^0.3964. All results are in m² and shown to three decimals.
How is the highlighted “Average BSA” worked out?
It is the plain mean of the three formula results. Averaging is this tool’s own choice and is not a published method. Clinical protocols normally name one formula, so use the individual line your protocol specifies and not the average.
Which units does it expect?
Weight in kilograms and height in centimetres. There are no pounds or inches options, so convert first. Entering pounds as kilograms would overstate BSA considerably.
Why do the three formulas disagree?
They were fitted to different groups of people. For a 70 kg, 175 cm adult they differ by under 0.01 m², but for 110 kg and 185 cm the tool shows 2.332 (DuBois), 2.378 (Mosteller) and 2.407 (Haycock). The gap widens at the extremes.
What is the “Adult range built into this tool” line?
It is a fixed text line in the output (1.5 – 2.0 m²) that does not change with the inputs. It is a label built into this tool, not a clinical standard, and the tool does not compare your result against it.
Is it suitable for children or for dosing?
Haycock’s equation was fitted on data that included infants and children, but the tool has no paediatric mode and takes no age. It does not calculate doses, apply capping or adjust for obesity. Any BSA-based dosing rule comes from the prescriber and local protocol.
What happens if weight or height is blank?
Clearing a box counts as 0 on this page, and a 0 for either weight or height produces a prompt asking for both. The message names the missing field. Zero and negative entries are not replaced with defaults.
Can it be used for dosing?
No. It only returns BSA figures from the numbers entered. A pharmacist or doctor confirms any BSA used for treatment.
Body surface area calculator — Mosteller, DuBois and Haycock side by side
Three equations, one set of measurements
Body surface area estimates the outer area of the body in square metres from height and weight. Mosteller takes the square root of height times weight divided by 3600, which is easy to check on a calculator. DuBois and Haycock use fractional powers of weight and height. This tool runs all three and then averages them, so you can see how far they disagree. Height goes in centimetres and weight in kilograms, and results are shown in square metres to three decimals, which is more precision than the underlying equations really support.
Three body sizes compared
The table lists the values returned for a medium, a small and a large adult. The 110 kg row shows the largest spread, with DuBois about 0.07 m² below Haycock; at 70 kg and 175 cm the three agree to the second decimal.
| Weight, height | Mosteller | DuBois | Haycock | Average |
|---|---|---|---|---|
| 70 kg, 175 cm | 1.845 | 1.848 | 1.847 | 1.847 |
| 55 kg, 160 cm | 1.563 | 1.563 | 1.566 | 1.564 |
| 110 kg, 185 cm | 2.378 | 2.332 | 2.407 | 2.372 |
Which number to use
The highlighted figure is the three-way average, a convenience this tool adds. If a care protocol says “Mosteller” or “DuBois”, take that line and ignore the average. The same applies if a drug reference caps BSA or uses actual versus ideal weight; the tool has no such options.
Things the tool does not do
It has no age input, no paediatric adjustment and no conversion from pounds or inches. It does not calculate any drug dose. The “Adult range built into this tool” line it prints is fixed wording and does not respond to your inputs. A weight or height of 0, which is what a cleared box becomes, returns an error naming the field. The input fields carry no suffix, so the units are only stated in their labels; double-check them before you copy a figure anywhere.
General information only
This page is general information, not medical advice and not for clinical decisions. A qualified clinician or pharmacist confirms the BSA and any resulting dose for a real patient.
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Results are estimates for informational purposes only and do not constitute professional financial, medical, legal, or technical advice. Read full disclaimer →