Body Surface Area Calculator - 8 Formulas, Free & Instant
Free Body Surface Area (BSA) calculator with Du Bois, Mosteller, Haycock, Boyd, and 5 more formulas. Supports metric & imperial units. Instant results in m², ft² & in² - perfect for chemotherapy dosing, GFR, and medical use.
Share Calculator
Common Calculators | |
Table of Contents
Body Surface Area (BSA) Calculator
Trying to figure out the right chemotherapy dose, burn treatment plan, or glomerular filtration rate (GFR)? You'll almost always need an accurate body surface area (BSA) value. Our free Body Surface Area Calculator instantly gives you results using eight of the most trusted formulas - Du Bois, Mosteller, Haycock, Gehan & George, Boyd, Fujimoto, Takahira, and Schlich - all in one click, with results in square meters, square feet, and square inches.
Just choose metric or imperial units, enter your height and weight, hit "Calculate," and you're done.
Why Body Surface Area Matters More Than Weight Alone
Doctors and researchers have known for over a century that many drugs and physiological processes don't scale linearly with body weight. A 6-foot adult and a small child who both weigh 70 kg (154 lb) will metabolize certain medications very differently because their skin surface - and therefore the distribution volume of many drugs - is not the same.
That's why oncology, nephrology, anesthesiology, burn units, and pediatric departments rely on BSA rather than simple weight when calculating:
Chemotherapy dosages (especially in pediatrics and high-dose regimens)
Cardiac index and glomerular filtration rate (eGFR)
Dialysis dosing
Steroid and antibiotic dosing in critical care
Fluid resuscitation in severe burns
Nutritional requirements in extreme body sizes
 Calculator.jpg "us calculator")
The Eight Most Common BSA Formulas Explained
Here's a quick look at each formula our calculator uses and where it shines:
| Formula | Year | Best For | Notes |
|---|---|---|---|
| Du Bois | 1916 | General adult use | The classic “gold standard” for decades |
| Mosteller | 1987 | Quick bedside calculation | Simple √(height × weight / 3600) - easy to remember |
| Haycock | 1978 | Pediatrics | Excellent accuracy in children |
| Gehan & George | 1970 | Oncology & research | Widely used in cancer studies |
| Boyd | 1935 | Historical reference | Complex logarithmic formula; still appears in some older protocols |
| Fujimoto | 1968 | Asian populations | Developed and validated in Japanese patients |
| Takahira | 1925 | Rarely used today | One of the earliest formulas |
| Schlich | 2010 | Modern European data | Separate equations for males and females (we use male default) |
How Accurate Are These Formulas?
For most adults, the Du Bois, Mosteller, Haycock, and Gehan & George formulas agree within 0.05-0.1 m². The Boyd formula often gives a noticeably higher value (around 6.4 m² for an average adult) because of its logarithmic component - you'll see this clearly in our calculator.
In real-world practice today:
Most oncology centers use Du Bois or Mosteller
Pediatric units prefer Haycock or Mosteller
Burn centers often stick with Du Bois
Normal Body Surface Area Ranges
| Group | Average BSA (m²) |
|---|---|
| Adult male (avg height/weight) | 1.9 - 2.0 |
| Adult female | 1.6 - 1.8 |
| 1.1 - 1.3 | 1.1 - 1.3 |
| Newborn | 0.2 - 0.25 |
Extremely tall or obese individuals can exceed 2.5 m², while very petite adults may fall below 1.5 m².
Quick Reference Table (Example Values)
Here's what our calculator shows for some common heights and weights:
| Height | Weight | Mosteller | Du Bois | Boyd | BMI |
|---|---|---|---|---|---|
| 5'9" (175 cm) | 155 lb (70 kg) | 1.85 m² | 1.85 m² | 6.41 m² | 22.9 |
| 5'2" (157 cm) | 120 lb (54 kg) | 1.57 m² | 1.57 m² | 5.51 m² | 21.9 |
| 6;2″ (188 cm) | 200 lb (91 kg) | 2.15 m² | 2.15 m² | 7.29 m² | 25.6 |
Frequently Asked Questions
Q: Which BSA formula is the most accurate?
A: There is no single “most accurate” formula for everyone. Mosteller and Du Bois are the most widely accepted in modern medicine because they're simple and well-validated across large populations.
Q: Why does the Boyd formula give such a high number?
A: The Boyd equation includes a logarithmic correction that produces values roughly 3-4 times higher than others. Some older literature used it, but it has largely been replaced.
Q: Should I cap BSA at 2.0 m² for chemotherapy like some hospitals do?
A: Some centers historically capped BSA at 2.0 m² to avoid toxicity in very large patients, but current guidelines (ASCO, ESMO) recommend using the actual calculated BSA without capping, especially with modern supportive care.
Q: Does body fat percentage affect BSA?
A: Yes, indirectly. People with higher body fat at the same height and weight will have slightly lower BSA because fat tissue has less surface area than lean tissue.