# Body Surface Area (BSA) Calculator

Calculate your body surface area using Mosteller, DuBois, and Haycock formulas. BSA is used for medication dosing, burn assessment, and physiological.

## What this calculates

Body Surface Area (BSA) is a measurement used in many medical calculations, including drug dosing, burn assessment, and physiological norms. Calculate your BSA using three widely accepted formulas from your weight and height.

## Inputs

- **Weight** (kg) — min 1, max 300
- **Height** (cm) — min 30, max 250

## Outputs

- **BSA (Mosteller)** — Body surface area using the Mosteller formula
- **BSA (DuBois & DuBois)** — Body surface area using the DuBois formula
- **BSA (Haycock)** — Body surface area using the Haycock formula
- **Average BSA** — Average of the three formulas

## Details

Body surface area is an important clinical parameter used more frequently than body weight for many medical calculations. Chemotherapy dosing, fluid requirements, cardiac output indices, and renal function assessments all commonly use BSA. The average adult BSA is approximately 1.7 m² for women and 1.9 m² for men.

The Mosteller formula is the simplest and most widely used: BSA = sqrt((height x weight) / 3600). The DuBois formula (1916) was historically the first and remains a reference standard. The Haycock formula was specifically developed with pediatric patients in mind and is often used for children.

All three formulas typically agree within 5% for adults of normal body composition. For obese individuals or children, the Haycock formula may be more appropriate. In clinical practice, BSA-based dosing helps normalize drug doses across patients of different sizes, providing more consistent therapeutic drug levels than weight-based dosing alone.

## Frequently Asked Questions

**Q: Why is BSA used instead of body weight for drug dosing?**

A: BSA correlates better than body weight with many physiological parameters including cardiac output, blood volume, glomerular filtration rate, and basal metabolic rate. Using BSA for drug dosing helps achieve more consistent drug plasma levels across patients of different sizes. This is particularly important for drugs with a narrow therapeutic index, such as chemotherapy agents, where small differences in dose can affect efficacy and toxicity.

**Q: Which BSA formula should I use?**

A: For most adults, the Mosteller formula is recommended due to its simplicity and accuracy. The DuBois formula is the most historically validated. The Haycock formula is preferred for pediatric patients. In practice, all three formulas produce similar results for normal-weight adults. Your healthcare provider will specify which formula they prefer for clinical calculations.

**Q: What is a normal body surface area?**

A: The average BSA for adult men is approximately 1.9 m², and for adult women approximately 1.7 m². BSA can range from about 1.2 m² for small adults to over 2.5 m² for very large individuals. A newborn has a BSA of approximately 0.25 m². BSA increases with both height and weight, but is more sensitive to changes in weight.

**Q: How is BSA used in burn assessment?**

A: In burn medicine, BSA is used to estimate the percentage of body surface affected by burns, which guides fluid resuscitation protocols like the Parkland formula. The Rule of Nines is a quick method to estimate burn extent, dividing the body into regions of approximately 9% of total BSA. Accurate BSA-based burn assessment is critical for calculating appropriate IV fluid volumes in the first 24-48 hours after a major burn.

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Source: https://vastcalc.com/calculators/health/body-surface-area
Category: Health & Fitness
Last updated: 2026-04-21