Calculate body surface area from metric or imperial height and weight using Mosteller, Du Bois, Haycock, or Gehan–George, with formula comparison, spread, ft², and BMI.
Medical note: This calculator provides an estimate only and is not medical advice. Do not use this result to adjust medication doses or make treatment decisions—clinical use of BSA (including dosing) should be determined by a licensed clinician, especially for children, pregnancy, kidney/liver disease, cancer treatment, or other medical conditions.
BSA Formula
The BSA calculator defaults to Mosteller and also offers Du Bois, Haycock and Gehan–George. Each uses height in centimeters and weight in kilograms and returns an estimate in square meters. The comparison and spread describe differences between formulas, not clinical accuracy.
- BSA = body surface area in square meters, m²
- W = weight in kilograms, kg
- H = height in centimeters, cm
- 3600 = Mosteller formula constant
If you enter weight in pounds, the calculator first converts pounds to kilograms:
If you enter height in inches, the calculator first converts inches to centimeters:
The calculator also converts the final BSA from square meters to square feet:
- Primary BSA result: uses the selected formula to estimate BSA in m²; Mosteller is the default.
- Measurements: accepts cm and kg in metric mode, or whole feet, additional inches and lb in imperial mode. Each system retains separate entered values.
- Square feet output: multiplies the m² result by 10.7639 to show BSA in ft².
Illustrative Mosteller Calculations
These are numerical input examples, not age-based reference ranges or clinical thresholds.
| Height / weight | Estimated BSA | Interpretation |
|---|---|---|
| 50 cm / 3.5 kg | 0.2205 m² | Illustrative inputs only |
| 100 cm / 20 kg | 0.7454 m² | Illustrative inputs only |
| 175 cm / 70 kg | 1.8447 m² | Illustrative inputs only |
| 190 cm / 100 kg | 2.2973 m² | Illustrative inputs only |
Common Unit Conversions for BSA Calculations
| Conversion | Formula | Example |
|---|---|---|
| Pounds to kilograms | lb × 0.45359237 | 150 lb = 68.0388555 kg |
| Inches to centimeters | in × 2.54 | 68 in = 172.72 cm |
| Square meters to square feet | m² × 10.7639 | 1.80 m² = 19.3750 ft² |
Example
Example 1: Calculate BSA for a person who weighs 70 kg and is 175 cm tall.
Converted to square feet:
Example 2: Calculate BSA for a person who weighs 150 lb and is 68 in tall.
First convert the inputs:
Then apply the Mosteller formula:
Converted to square feet:
FAQ
What is BSA?
BSA means body surface area. It is an estimate of the total external surface area of the body. BSA is often used in medical and health-related calculations because it can better reflect body size than weight alone.
Which BSA formula does this calculator use?
Mosteller is the default. You can select Du Bois, Haycock or Gehan–George, and compare all four estimates in Calculation details. Formula choice for clinical use requires a qualified clinician. See eviQ formula documentation.
Why are height and weight converted before calculating BSA?
The Mosteller formula used here requires weight in kilograms and height in centimeters. If you enter pounds or inches, those values must be converted first so the formula uses the correct units.
