Body Surface Area (BSA) Calculator

Enter your weight and height to calculate your body surface area (BSA) using both the Du Bois and Mosteller formulas — widely used in clinical drug dosing and metabolic assessments.

Created by Luis GonzalezLast updated: May 9, 2026

How to Use This Calculator

1
Enter your Weight
Input your current weight in pounds. For an adult, this might range from 100 to 300 lbs.
2
Enter your Height
Provide your height in inches. A typical adult height falls between 60 and 75 inches.
3
Review your results
The calculator displays six cards: BSA (Du Bois), BSA (Mosteller), Average BSA, Formula Difference, BMI, and Weight in kg.

Example Calculation

A healthcare professional needs to calculate Body Surface Area for a patient weighing 170 lbs and standing 70 inches tall to determine precise medication dosages.

Weight

170

Height

Results

BSA (Du Bois)

1.948 m², BSA (Mosteller): 1.952 m², Average BSA: 1.950 m², Formula Difference: 0.0035 m², BMI: 24.4, Weight in kg: 77.1 kg

Tips

Consider the Formula Differences

While both Du Bois and Mosteller formulas are widely used, they can produce slightly different results. For an average adult, the difference is often less than 0.05 m², but for extreme body types, the variance can be more significant.

Accuracy in Measurement

Ensure precise measurements for weight and height. Even a 1-inch error in height or a 5-pound error in weight can alter BSA by approximately 0.02-0.03 m², potentially impacting critical dosage calculations.

Clinical vs. General Use

In clinical settings, BSA is often rounded to two decimal places for consistency in dosing, particularly for chemotherapy, where a 0.01 m² difference can mean a milligram adjustment in medication.

Body Surface Area (BSA) is a calculated measurement representing the total surface area of a human body. This metric is frequently used in medicine, particularly in pharmacology, where it helps determine accurate drug dosages for treatments like chemotherapy. For instance, an average adult BSA typically falls within the range of 1.7 to 2.0 square meters, but this can vary significantly based on individual height and weight. Calculating BSA provides a standardized way to dose medications that account for individual differences in metabolism and distribution.

The Mathematical Foundation of Body Surface Area Calculation

Calculating Body Surface Area involves specific mathematical formulas that relate a person's weight and height to their total external surface. These formulas convert the raw input values into a two-dimensional area. The calculator first converts your weight from pounds to kilograms and your height from inches to centimeters, as these are the standard units for the BSA formulas.

The Du Bois formula, established in 1916, is one of the oldest and most widely recognized:

BSA (Du Bois) = 0.007184 × weight_kg^0.425 × height_cm^0.725

Here, weight_kg is your weight in kilograms and height_cm is your height in centimeters.

The Mosteller formula, developed in 1987, offers a simpler calculation and is also frequently used:

BSA (Mosteller) = √((weight_kg × height_cm) / 3600)

In this formula, weight_kg and height_cm represent the same values as above. The constant 3600 is derived from statistical analysis to normalize the result into square meters.

💡 Understanding complex mathematical relationships like those in BSA formulas can be challenging. If you enjoy breaking down numerical problems, our 24 Game Solver can provide a fun way to practice mental math and logical reasoning.

Calculating Body Surface Area for a Patient

Consider a healthcare professional needing to determine the Body Surface Area for a patient to accurately dose a medication. The patient weighs 180 lbs and is 68 inches tall.

Here's how the calculation proceeds:

Convert Weight to Kilograms: The patient's weight of 180 lbs is converted to kilograms: 180 lbs × 0.453592 kg/lb = 81.64656 kg.
Convert Height to Centimeters: The patient's height of 68 inches is converted to centimeters: 68 in × 2.54 cm/in = 172.72 cm.
Calculate BSA using Du Bois formula: BSA (Du Bois) = 0.007184 × (81.64656)^0.425 × (172.72)^0.725 BSA (Du Bois) ≈ 0.007184 × 6.848 × 39.544 ≈ 1.95 m²
Calculate BSA using Mosteller formula: BSA (Mosteller) = √((81.64656 × 172.72) / 3600) BSA (Mosteller) = √(14109.81 / 3600) = √(3.919) ≈ 1.98 m²

The patient's Body Surface Area is approximately 1.95 m² (Du Bois) and 1.98 m² (Mosteller). These values are then used to scale medication dosages.

💡 Accurate medical calculations often depend on understanding how individual measurements contribute to a final metric. If you're working with data distributions in a health context, our Standard Deviation Z-Score Table can help you analyze how a patient's measurement compares to a population mean.

Manual Calculation Walkthrough

To understand the mechanics behind the Body Surface Area calculation, let's walk through it manually for an individual weighing 150 lbs and standing 65 inches tall.

Convert Weight: Weight in kg = 150 lbs × 0.453592 = 68.0388 kg
Convert Height: Height in cm = 65 in × 2.54 = 165.1 cm
Apply Du Bois Formula: First, calculate the exponential terms: 68.0388^0.425 ≈ 6.130 165.1^0.725 ≈ 37.668 Then, multiply: BSA (Du Bois) = 0.007184 × 6.130 × 37.668 ≈ 1.66 m²
Apply Mosteller Formula: First, multiply weight and height: 68.0388 kg × 165.1 cm = 11233.10988 Then, divide by 3600 and take the square root: BSA (Mosteller) = √(11233.10988 / 3600) = √(3.1203) ≈ 1.76 m²

This step-by-step process demonstrates how the raw measurements are transformed into the final BSA values.

What body surface area (bsa) results look like in practice

Body Surface Area (BSA) values vary across different populations and are interpreted differently depending on the clinical context. For an average adult, BSA typically ranges from 1.7 m² to 2.0 m². In oncology, for instance, chemotherapy dosages are often standardized to 1.5 m² for women and 1.8 m² for men, serving as common reference points before individual adjustments. Pediatric BSA values are considerably lower, with a newborn's BSA being around 0.25 m², and a 10-year-old child's BSA averaging 1.07 m². For burn patients, BSA is critical for fluid resuscitation, where the Parkland formula dictates fluid volume based on the percentage of body surface area burned, often measured in increments of 9% for adults (Rule of Nines). In cardiology, a cardiac index, which measures heart performance, is calculated by dividing cardiac output by BSA, with a normal range typically between 2.5 and 4.0 L/min/m². These benchmarks illustrate how BSA is a foundational metric in various medical disciplines, guiding critical decisions.

Frequently Asked Questions

Why are there different formulas for calculating Body Surface Area?

Various BSA formulas exist because they were developed using different populations and methodologies, aiming to provide the most accurate estimate. The Du Bois formula, for instance, was derived in 1916 from a small group, while Mosteller's, from 1987, is simpler and widely adopted for its accuracy across a broader range of body types. Differences in results are usually minor, often within 0.05 m² for adults.

How is Body Surface Area (BSA) used in medical treatments?

BSA is a crucial metric in medicine, especially for calculating drug dosages, particularly for chemotherapy, where drugs are potent and require precise administration. It's also used in fluid resuscitation for burn victims and in determining cardiac index. For example, many chemotherapy protocols dose drugs based on mg/m² of BSA, ensuring a consistent effect relative to patient size.

Does Body Surface Area change significantly with minor weight fluctuations?

Body Surface Area does not change dramatically with minor weight fluctuations. A 5-pound change in an adult's weight (e.g., from 150 lbs to 155 lbs for someone 67 inches tall) would typically alter their BSA by less than 0.02 m². Significant changes in weight or height, such as during growth spurts in children or substantial weight loss/gain in adults, lead to more noticeable BSA variations.