Enter height and weight into the calculator (the Du Bois formula shown below uses height in centimeters (cm) and weight in kilograms (kg), and this calculator will handle unit conversions). The calculator will estimate Body Surface Area (BSA), sometimes also called “skin area.” 

Body Surface Area (BSA) Calculator

Enter any 2 values to calculate the missing variable

Important: This calculator is for education only and is not medical advice. Do not use it to self-dose or make treatment decisions. Medication dosing is patient- and protocol-specific (often including rounding rules, maximum-dose caps, and organ function adjustments) and should be verified by a licensed clinician/pharmacist and the medication label/protocol.

Body Surface Area (BSA) Formula

SA = 0.007184 * H^{0.725} * W^{0.425}

Variables:

  • SA is the body surface area (BSA) (m^2)
  • H is the height (cm)
  • W is the weight (kg)

To calculate BSA, raise the height (in cm) to .725, then multiply by the weight (in kg) raised to .425, then multiply the result by .007184.

How to Calculate Body Surface Area (BSA)?

The following steps outline how to calculate the body surface area (BSA).

  1. First, determine the height (cm). 
  2. Next, determine the weight (kg). 
  3. Next, gather the formula from above = SA = .007184 * H^.725 * W^.425 (with H in cm and W in kg).
  4. Finally, calculate the body surface area (BSA).
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

height (cm) = 175 (1.75 m)

weight (kg) = 78

Context: typical adult BSA values are often around ~1.5–2.2 m² (individual results vary by height/weight and formula).

Frequently Asked Questions (FAQ)

What is the purpose of calculating body surface area (BSA)?

BSA is an estimated measurement used in some clinical and research contexts. For example, clinicians may use BSA as one of several factors when considering dosing for certain medications, and it may be used in some physiological assessments.

How accurate is the BSA formula?

BSA formulas such as the Du Bois & Du Bois equation (shown above) and the Mosteller equation provide estimates that are widely used. Accuracy can vary by individual characteristics and may be less reliable at extremes of body size.

Can I use the BSA formula for children?

These formulas can be used for children, but pediatric care often follows age- and condition-specific guidance. Clinicians may choose alternative pediatric-focused formulas depending on context.

Are there any limitations to using BSA?

Yes. BSA is an estimate and may be less accurate in situations such as extreme obesity/underweight, fluid overload/edema, pregnancy, or other special circumstances. If you’re using BSA in a clinical context, follow institutional protocols and consult a licensed clinician.