Free Body Surface Area (BSA) Calculator

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Based on peer-reviewed medical formulas.

Enter Your Details

Weight (kg)

Height (cm)

0.00

m² (Mosteller Formula)

DuBois Formula

0.00 m²

⚠ For information only — this is an estimate, not a medical measurement. Clinicians sometimes use BSA for drug dosing; never use it to self-dose any medication. Discuss clinical questions with a qualified healthcare provider.

Why Doctors Care About Surface Area at All

It sounds like an anatomy-class puzzle, but your surface area turns out to be a surprisingly useful clinical number. Body Surface Area (BSA) is the total surface area of the human body measured in square meters. It provides a more accurate representation of metabolic mass than body weight alone because it accounts for both height and weight proportionally. BSA is widely used in clinical medicine, pharmacology, and physiology to calculate drug dosages, assess metabolic rate, and evaluate organ function.

The concept of BSA was first introduced in the early 1900s and has since become a standard measurement in healthcare. The average adult male BSA is approximately 1.9 m², while the average adult female BSA is approximately 1.6 m². These values vary significantly with height, weight, age, and body composition.

Chemo Dosing, Drug Dosing, and BSA

Average Male

~1.9 m²

Average Female

~1.6 m²

The most headline-worthy use is oncology: BSA is central to numerous clinical applications, most notably for calculating chemotherapy dosages. Many cytotoxic drugs are prescribed on a per-square-meter basis to ensure proportional dosing across patients of different sizes. This approach minimizes the risk of underdosing in smaller patients and overdosing in larger ones.

Drug dosing — Chemotherapy, cardiac medications, and pediatric drugs are often dosed per m² of BSA.
Burn assessment — The Rule of Nines and Lund-Browder chart use BSA to estimate burn severity.
Cardiac index — Cardiac output is divided by BSA to calculate cardiac index, a key heart function metric.
GFR estimation — Glomerular filtration rate uses BSA to normalize kidney function measurements.

The Du Bois and Mosteller Equations Compared

Don't expect one tidy answer for everyone — BSA varies significantly between individuals based on their body proportions. The Mosteller formula, which this calculator uses as its primary method, is the simplest and most widely accepted BSA estimation: BSA (m²) = v((height cm × weight kg) / 3600). This formula provides reliable estimates for the majority of the population.

The DuBois formula offers an alternative calculation that may be slightly more accurate at extreme body sizes: BSA = 0.007184 × height^0.725 × weight^0.425. Both formulas are included in this calculator so you can compare results and see the range of estimated values. Consult your healthcare provider for clinically precise BSA measurements. You can also check your BMI and body fat percentage for a complete health picture.

What a Normal BSA Range Looks Like

Flat numbers only mean something in context. For a typical healthy adult, BSA lands between roughly 1.4 and 2.2 m² — averaging about 1.9 m² for men and 1.6 m² for women. Because BSA tracks closely with height and weight, taller and heavier people will naturally sit higher in that range, and children sit low while still being perfectly healthy.

Rather than chasing a single "ideal" number, use yours to understand why a doctor might dose a drug per m² (so a larger person gets a proportionally larger dose) and why the same medication can be perfectly appropriate at very different milligram doses in two different people. Your value is a relative index, not a pass/fail score.

Frequently Asked Questions

What does a typical BSA look like?

The average adult male BSA is approximately 1.9 m², and the average adult female BSA is approximately 1.6 m². Normal range for healthy adults typically falls between 1.4 and 2.2 m² depending on height and weight.

What math sits behind a BSA figure?

The most common method is the Mosteller formula: BSA (m²) = square root of ((height in cm × weight in kg) / 3600). Other formulas include DuBois, Haycock, and Shuter, each with slightly different coefficients.

Why bother calculating BSA at all?

Doctors use BSA for calculating drug dosages, especially for chemotherapy, pediatric medications, and cardiac medications. BSA provides a more accurate measure of metabolic mass than body weight alone, leading to safer and more effective dosing.

How does your BSA change the dose you're given?

Many medications, particularly chemotherapy drugs, are dosed per square meter of BSA. A patient with a larger BSA may receive a higher dose than someone smaller, ensuring proportional drug distribution across different body sizes and improving treatment safety.

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