Body Surface Area Calculator
Du Bois and Mosteller body surface area from height and weight.
What it does
Body surface area estimates the skin area from height and weight. Oncology, burn care, and physiology scale some doses and measures to surface rather than weight alone, because heat loss and exposure follow area more closely.
The tool above takes height and weight in metric or imperial. It returns the Du Bois value as the main answer with the Mosteller value beside it for cross checking, plus square feet for reference.
The default example of 70 kg at 175 cm gives 1.85 m² Du Bois against 1.84 m² Mosteller (19.89 ft²). The imperial mirror of 154 lb at 69 in lands at 1.85 and 1.84 m² as well, showing the conversion path holds.
Du Bois and Du Bois published the 1916 height weight formula from direct measurements, and NCI drug dictionaries plus the National Library of Medicine still reference BSA based dosing today. Mosteller offered the simpler root form in 1987 for ward math.
How to use
- Pick metric or imperial first.
- Enter height without shoes and morning weight.
- Read Du Bois first, since most protocols name it.
- Compare Mosteller beside it; gaps over a few percent deserve remeasuring.
- Hand the pair to the clinician instead of dosing from the page.
Formula
- 0.007184
- Du Bois constant fitting measured surfaces.
- 0.425 / 0.725
- Powers weighting weight and height.
- 3600
- Mosteller divisor pairing cm with kg.
Imperial inputs convert first (1 in = 2.54 cm, 1 lb = 0.45359237 kg), then run the same metric formulas, so both systems agree. Extreme builds drift because the 1916 sample centered on typical adults.
Worked example
Example: 70 kg at 175 cm
Metric defaults: 175 cm, 70 kg.
- Powers: 70^0.425 = 6.078, 175^0.725 = 42.27.
- Multiply: 0.007184 x 6.078 x 42.27 = 1.8481.
- Round: 1.85 m² Du Bois.
- Mosteller: root(175 x 70 / 3600) = root(3.4028) = 1.84 m².
- Square feet: 1.8481 x 10.7639 = 19.89 ft². Tool shows 1.85 m², 1.84 m², 19.89 ft².
Reference table
| Build | Du Bois | Context |
|---|---|---|
| 60 kg, 165 cm | about 1.66 m² | Small adult |
| 70 kg, 175 cm | 1.85 m² | Example here |
| 80 kg, 180 cm | about 2.00 m² | Large adult |
| 100 kg, 190 cm | about 2.28 m² | Very large adult |
Limits
- Estimate only, never a dosing order by itself.
- Fitted on typical adults; obesity and infancy drift.
- Tape and scale error move the answer directly.
- Protocols name one formula; mixing them across visits breaks trends.
Common mistakes
- Entering pounds into the kg slot without converting.
- Using evening weight with shoes for a dosing number.
- Quoting BSA to three decimals as if skin were machined.
- Swapping Du Bois and Mosteller mid treatment.
- Dosing from the page instead of the protocol sheet.
Try it yourself
Quick checks. Answers sit tucked under each question.
Mosteller for 180 cm and 80 kg?
root(180 x 80 / 3600) = root(4) = 2.00 m².
Imperial check: 154 lb at 69 in?
Converts to 69.85 kg and 175.26 cm, giving 1.85 m² Du Bois and 19.9 ft².
Small adult 60 kg at 165 cm?
Du Bois near 1.66 m², Mosteller near 1.66 m².
Questions
What is a normal BSA?
Most adults sit between 1.4 and 2.2 m², with 1.73 m² a classic reference adult.
Du Bois or Mosteller?
Du Bois is the historic standard, Mosteller the simple check. They agree within a few percent typically.
Why dose by surface?
Some drugs and burns scale with exposure and loss, which follow area better than weight.
How precise are inputs?
Half a centimeter and half a kilo are plenty; finer digits outrun tape accuracy.
Does muscle change it?
Only through weight. Two people at 80 kg share the formula even with different builds.
Can I use this for children?
Pediatric protocols use their own tables and checks. Confirm with the care team.