This body surface area calculator estimates BSA with the Mosteller formula: square root of (weight kg × height cm) / 3600. The default values weight 70 kg and height 175 cm return about 1.845 m².
It is a quick educational estimate for coursework and unit practice. Energy and macro tools that also use height and weight include the TDEE calculator and the protein calculator.
How the formula works
Multiply weight in kilograms by height in centimeters. Divide by 3600. Take the positive square root. The result is Mosteller BSA in square meters.
Worked example
70 × 175 = 12250. Divide by 3600 to get about 3.40278. Square root yields about 1.8447, reported here as about 1.845 m².
| Input | Value |
|---|---|
| Weight | 70 kg |
| Height | 175 cm |
| (w × h) / 3600 | about 3.40278 |
| BSA (Mosteller) | about 1.845 m² |
How to use the fields
- Weight (kg) is body mass in kilograms.
- Height (cm) is stature in centimeters.
Unit conversion before you start
If height is 5 ft 9 in, convert to centimeters first. If weight is in pounds, convert to kilograms. Mixing imperial inputs into kg and cm fields will distort BSA badly.
Write the converted values in your notes so a reviewer can see the unit path, not only the final square meters.
Common mistakes
- Entering height in meters (1.75) instead of centimeters (175)
- Leaving weight in pounds while the field expects kilograms
- Forgetting the divide by 3600 step in hand work
- Treating BSA as a diagnosis rather than a geometric estimate
Sensitivity to height and weight
Because the formula uses a square root of a product, raising either input raises BSA, but not linearly. Doubling weight does not double BSA. Exploring that curve is a good lab question.
Hold height fixed and change weight by 5 kg steps to see the smooth rise in m².
Educational context only
Some clinical worksheets reference BSA. This calculator does not select drugs, doses, or care plans. It only evaluates Mosteller from the two anthropometric inputs.
When you cite a BSA number in homework, name Mosteller explicitly so readers know which formula produced it.
Comparing formulas in class
Du Bois and Mosteller can disagree by small amounts. If your course compares them, compute Mosteller here and keep the other formula on paper. Do not assume one tool covers every named equation.
Measurement quality
Morning weight, clothing, and stadiometer technique all move inputs. Tape height carefully and use a consistent weighing routine when you compare BSA across dates.
Rounding height to the nearest centimeter is usually enough for example work. Unrealistic precision in the inputs does not create clinical certainty in the output.
Reporting style
State weight, height, formula name, and BSA together. Example: 70 kg, 175 cm, Mosteller, about 1.845 m². That package is auditable.
Classroom drills
Ask students to estimate whether 80 kg at the same height raises BSA by more or less than 0.1 m², then confirm. A second drill converts a foot inch height, recomputes, and checks unit discipline.
Have pairs swap inputs and recompute to catch transcription errors early.
Same person, unit check
Convert 70 kg and 175 cm to other unit systems on paper, then convert back and rerun. If BSA jumps after a round trip, the conversion was wrong, not the Mosteller step. That drill builds unit confidence before any clinical discussion in a course setting.
Keep a one line template: weight kg, height cm, product, divide by 3600, square root, BSA m².
Pediatric versus adult examples
Course packets sometimes mix child and adult anthropometrics. Do not reuse an adult default without changing both inputs. Small height changes still move BSA because height sits inside the product under the square root.
Always restate age group assumptions in prose even though age is not a field on this calculator.
Limitations
Mosteller is an estimate from two measurements. It does not image the body, adjust for amputation, or replace clinical protocols. Educational use only.