Body Surface Area
Compute Body Surface Area with exact geometric formulas. Enter the required dimensions to see area, perimeter, or volume alongside step-by-step
Formula
BSA = √(height × weight / 3600)
The Mosteller formula calculates body surface area in square meters from height (cm) and weight (kg). Other formulas like Du Bois use different mathematical approaches.
Worked Examples
Example 1: Mosteller Formula
Problem:Calculate BSA for a person 180cm tall and 80kg.
Solution:Mosteller Formula:\nBSA = √(height × weight / 3600)\n\nBSA = √(180 × 80 / 3600)\nBSA = √(14400 / 3600)\nBSA = √4\nBSA = 2.00 m²\n\nThis is slightly above average adult BSA.
Result:BSA = 2.00 m² (Large category)
Example 2: Du Bois Formula
Problem:Same person using Du Bois formula.
Solution:Du Bois Formula:\nBSA = 0.007184 × height^0.725 × weight^0.425\n\nBSA = 0.007184 × (180)^0.725 × (80)^0.425\nBSA = 0.007184 × 43.18 × 6.44\nBSA ≈ 2.00 m²\n\nFor typical adults, Du Bois and Mosteller usually land very close to each other.
Result:BSA ≈ 2.00 m² (Du Bois)
Example 3: Chemotherapy Dosing Example
Problem:A drug is prescribed at 75 mg/m². Patient BSA is 1.85 m². What's the dose?
Solution:Dose = Prescribed dose per m² × BSA\n\nDose = 75 mg/m² × 1.85 m²\nDose = 138.75 mg\n\nIn practice, this might be rounded to 140 mg.\n\nThis is why accurate BSA matters: a 10% error in BSA causes 10% error in drug dose, which can be significant for toxic drugs.
Result:Dose = 138.75 mg (round to 140 mg)
Frequently Asked Questions
What is body surface area (BSA)?
Body surface area is the total surface area of the human body, measured in square meters (m²). Average adult BSA is approximately 1.7-2.0 m². BSA is used in medicine to normalize physiological parameters and drug dosages that vary with body size.
Does BSA change with body composition?
BSA formulas use only height and weight, not body composition. A muscular person and an obese person of the same height and weight would have identical calculated BSA, though their actual surface areas may differ. For extreme body compositions, adjustments may be needed.
What is body composition and why is it better than BMI alone?
Body composition describes what your body is actually made of: skeletal muscle, fat mass, bone mineral density, and water. Unlike BMI — which divides weight by height squared and cannot distinguish a pound of muscle from a pound of fat — body composition identifies whether weight is metabolically active tissue or stored energy. Healthy body fat percentages vary by sex and age: for women, 20-32% is generally considered healthy; for men, 8-19%. Measurement methods include DEXA scans (most accurate, ±1-2%), hydrostatic weighing, Bod Pod air displacement, bioelectrical impedance (consumer scales, ±3-5%), and skinfold calipers. A muscular person with a BMI of 27 (overweight) might have excellent body composition, while a sedentary person with a normal BMI could have metabolically risky visceral fat levels.