Body Surface Area Calculator
Calculate body surface area with the Mosteller, Du Bois, Haycock, Gehan-George and Boyd equations, and see how far apart they are.
Result
Enter height and weight to see the result.
https://calcgallery.com/body-composition/body-surface-area-calculator/
How to use the Body Surface Area Calculator
- Enter your height in feet and inches or in centimetres.
- Enter your weight in pounds or kilograms.
- Read the Mosteller result, then compare the other four beside it.
- Check the spread. It is how much the five published equations disagree at your size.
How it is calculated
Body surface area is the total area of the outside of the body. It cannot be measured directly without wrapping someone, so it is predicted from height and weight. Five published equations do that, all taking height in centimetres and weight in kilograms and returning square metres:
| Equation | Year | Form |
|---|---|---|
| Du Bois & Du Bois | 1916 | 0.007184 × H^0.725 × W^0.425 |
| Boyd | 1935 | 0.0003207 × H^0.3 × (W in grams)^(0.7285 − 0.0188 log₁₀ W in grams) |
| Gehan & George | 1970 | 0.0235 × H^0.42246 × W^0.51456 |
| Haycock | 1978 | 0.024265 × H^0.3964 × W^0.5378 |
| Mosteller | 1987 | √(H × W ÷ 3600) |
Mosteller is shown first because it is the one a person can check. The square root of height times weight over 3600 is arithmetic anyone can repeat, which is a real advantage for a number used in clinical settings where a silent error matters.
Boyd’s equation is the awkward one. Its exponent is itself a function of weight, and that weight is in grams, not kilograms. Passing kilograms produces about 0.03 m² instead of about 2.00 — an error large enough to be obvious once seen and completely invisible if the formula is simply copied. It is pinned here by its own test vector for that reason.
Where the five disagree. For an adult of average build they sit within roughly one percent of each other, and choosing between them changes very little. In the paediatric range the spread widens considerably, because the original measurement sets were mostly of adults. This calculator reports that spread as its own output, so the range is visible rather than hidden behind whichever equation happened to be shown.
This page computes an area. It does not compute a medication dose, and it must not be used as though it did. Dosing is a clinical calculation involving the drug, the protocol, the patient and a great deal that is not height and weight.
Practical tips
Use one equation consistently. If you are comparing a figure over time or against a reference table, switching equations introduces a difference that has nothing to do with the body.
Check Mosteller by hand. Height times weight, divide by 3600, square root. If a result from anywhere disagrees with that by more than a few percent, something has gone wrong in the entry rather than in the equation.
Treat small-body results with more caution. The equations were fitted mostly on adults, and their disagreement at paediatric sizes is a fair signal of how much confidence any single one deserves there.
The spread is information, not noise. Five published equations landing within 0.02 m² of each other is a strong result; five landing 0.03 m² apart on a body a third of the size says the prediction is doing more work.
Surface area is not a measure of health. It is geometry. It appears in dosing and in some physiological indices because rates scale with area, not because a larger or smaller area means anything on its own.
With your numbers
- The five equations span 0.019 m², from 1.629 m² to 1.648 m²
- Mosteller: √(162.6 cm × 59 kg ÷ 3600) = 1.63 m²
Quick reference
Five published equations that disagree, most of all at small body sizes. This page computes an area and never a dose.
| Example | BSA, Mosteller |
|---|---|
| 5 ft 4 in, 130 lb | 1.63 m² |
| 5 ft 8 in, 160 lb | 1.87 m² |
| 5 ft 10 in, 180 lb | 2.01 m² |
| 6 ft 0 in, 200 lb | 2.15 m² |
| 160 cm, 55 kg | 1.56 m² |
| 178 cm, 80 kg | 1.99 m² |
| 185 cm, 95 kg | 2.21 m² |
| 100 cm, 16 kg | 0.67 m² |
Common questions about the Body Surface Area Calculator
- Which formula do hospitals use?
- Mosteller is the most common in practice, largely because it is the only one that can be worked out on paper or checked mentally, which matters when a number is being verified at a bedside. Du Bois remains the reference against which later equations were compared. Individual institutions and protocols specify their own, so the honest answer is that it depends on the protocol rather than on which is most accurate.
- Why do the five results differ?
- Each was fitted to a different set of directly measured bodies, decades apart, using different measurement techniques. Du Bois and Du Bois worked from nine subjects in 1916. Boyd assembled a much larger set in 1935. Haycock fitted his specifically to include children. They agree closely for average adults, which is where most of the data sat, and diverge where the data was thin.
- Where do they disagree most?
- At small body sizes. For an adult of average build the five sit within about one percent of each other. For a small child the spread is proportionally several times larger, because most of the original measurements were of adults. That is why Haycock exists and why this page reports the spread rather than a single number.
- Does body surface area change with body composition?
- These equations cannot see composition. They take height and weight only, so a muscular person and a person carrying the same weight as fat receive the same surface area. Surface area is a geometric quantity about the outside of the body, and height and weight predict it well enough that adding composition has not been shown to be worth the extra measurement.
- Why is it reported in square metres even in the US?
- Because every source, reference table and protocol that uses body surface area expresses it that way. Converting to square feet would produce a number that is correct but that nobody working with this quantity would recognise or be able to compare against anything.