BSA Calculator

Category: Vital Signs & Health Indicators

- April 12, 2025

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Calculate Body Surface Area with different formulas

Metric (cm/kg)

Imperial (in/lb)

Height

Weight

Formula Options

Calculation Formula

Body Surface Area (BSA)

0.00 m²

Using DuBois & DuBois formula

Compare Different Formulas

Formula	BSA Result	Difference
DuBois & DuBois	0.00 m²	-
Mosteller	0.00 m²	0.0%
Haycock	0.00 m²	0.0%
Gehan & George	0.00 m²	0.0%
Boyd	0.00 m²	0.0%

Common BSA Applications

Drug Dosing

For medications dosed by BSA, calculate dose with:
Dose = BSA (m²) × Drug Dosage Factor

Cardiac Index

For a typical cardiac output of 5.0 L/min:
Cardiac Index = 5.0 ÷ BSA (m²) = 0.00 L/min/m²

Fluid Requirement

For burn patients, calculate 24-hour fluid requirement:
Fluid (mL) = BSA (m²) × 1500 = 0 mL

What is Body Surface Area (BSA)?

Body Surface Area (BSA) is the measured or calculated surface area of the human body. It is widely used in medicine for various clinical applications, including drug dosing, burn assessment, cardiac output measurements, and more.

Why is BSA important?

BSA correlates better with many physiological parameters than body weight alone. For example:

Many physiological functions like cardiac output, blood volume, and renal function correlate better with BSA than with weight
BSA-based dosing helps adjust drug doses more appropriately than weight alone, especially for drugs with narrow therapeutic windows
BSA provides a standardized way to compare individuals of different sizes

Normal BSA Values

The average adult has a BSA of approximately 1.7 m² (1.6 m² for women, 1.9 m² for men), but this varies considerably with height and weight. Children have progressively smaller BSA values corresponding to their size.

Note: While widely used, BSA formulas are approximations. Different formulas may yield slightly different results, and all are estimations of the true surface area of the human body.

BSA Calculation Formulas

Several formulas have been developed to estimate BSA. Each uses a different mathematical approach, which may yield slightly different results:

DuBois & DuBois (1916)

BSA (m²) = 0.007184 × Height(cm)^0.725 × Weight(kg)^0.425

The most widely used formula in clinical practice. Generally accurate for most adults.

Mosteller (1987)

BSA (m²) = √[(Height(cm) × Weight(kg)) ÷ 3600]

A simplified formula that is easier to calculate and remember. Accurate across a wide range of body sizes.

Haycock (1978)

BSA (m²) = 0.024265 × Height(cm)^0.3964 × Weight(kg)^0.5378

Commonly used for pediatric patients. More accurate for children than some other formulas.

Gehan & George (1970)

BSA (m²) = 0.0235 × Height(cm)^0.42246 × Weight(kg)^0.51456

Developed to improve accuracy across a wide range of heights and weights.

Boyd (1935)

BSA (m²) = 0.0003207 × Height(cm)^0.3 × Weight(g)^{0.7285 - (0.0188 × log(Weight(g)))}

A more complex formula that may be more accurate for certain body types. Weight is in grams for this formula.

Which Formula Should I Use?

The DuBois & DuBois formula is the most widely used in clinical practice, but each formula has its strengths:

For general use: DuBois & DuBois or Mosteller
For pediatrics: Haycock or Mosteller
For research: Consider comparing multiple formulas

Important Note:

For clinical applications like drug dosing, always use the same formula consistently. Different formulas can give results that vary by 5-10%, which could impact drug dosages or other clinical calculations.

Clinical Applications of BSA

Body Surface Area is used in numerous medical contexts:

1. Drug Dosing

Many medications, especially chemotherapy drugs, are dosed according to BSA to standardize doses across patients of different sizes. This helps achieve therapeutic blood levels while minimizing toxicity.

General Formula: Drug Dose = Drug Dosage Factor × BSA (m²)

Example: If a chemotherapy drug is prescribed at 100 mg/m², a patient with a BSA of 1.8 m² would receive: 100 mg/m² × 1.8 m² = 180 mg

2. Cardiac Function Assessment

Cardiac output is often indexed to BSA (called the Cardiac Index) to allow for comparison between individuals of different sizes.

Cardiac Index = Cardiac Output (L/min) ÷ BSA (m²)

Normal values: 2.5-4.0 L/min/m²

3. Burn Assessment

The "Rule of Nines" and other burn assessment tools use BSA to estimate the percentage of body affected by burns.

Parkland Formula for fluid resuscitation:
Fluid in first 24 hours (mL) = 4 × BSA burned (%) × Weight (kg)

4. Renal Function

Glomerular filtration rate (GFR) is often normalized to BSA to allow comparison between individuals:

Normalized GFR = Measured GFR × (1.73 m² ÷ Patient's BSA)

1.73 m² is the standard BSA for GFR normalization

5. Basal Metabolic Rate

BSA correlates with metabolic rate and is sometimes used in equations to estimate energy requirements.

6. Equipment Sizing

Medical equipment such as oxygenators, dialyzers, and ECMO circuits may be sized according to BSA.

Limitations:

BSA-based calculations may not be appropriate for patients at extremes of height or weight, very muscular individuals, or those with conditions affecting body composition. Clinical judgment should always be used alongside BSA-based calculations.

Crunching the Numbers: Why the BSA Calculator is Your Handy Health Helper

The BSA Calculator is a smart little tool that figures out your Body Surface Area, or BSA for short. That’s just a fancy way of measuring how much space your body takes up on the outside. Sounds simple, right? But this number is actually super useful in healthcare.

Doctors often use BSA to make sure medicine doses are just right. Too much could be harmful. Too little might not work. It’s also used in heart tests, burn care, and planning fluids for people who are very sick. With the BSA Calculator, you can skip the long math and get results in seconds.

Let’s be real—doing all that math by hand can feel like a bombastic headache. This calculator cuts right through the stress.

What It Can Do for You

Here’s what the BSA Calculator can do:

⚖️ Switch between metric (cm/kg) and imperial (in/lb) depending on how you measure height and weight.
🧮 Calculate BSA using five different formulas, including DuBois, Mosteller, and Boyd.
📊 Compare results across formulas to see how they differ.
💊 Help with things like drug dosing, heart tests, and fluid planning.

You even get bonus info like charts and sample calculations. It's all packed into one neat calculator box—no need to bounce around the internet looking for answers.

Real-Life Perks of Using It

You don’t have to be a doctor to find this calculator helpful. Here are some ways it fits into everyday life:

School project on human biology? Use the calculator to explain BSA in a cool way.
Training to be a nurse or med student? Practicing dosage calculations with real numbers makes learning easier.
Helping care for someone at home? Use it to understand fluid needs or health stats your doctor mentions.

Here’s an example:

Let’s say your friend weighs 70 kg and is 175 cm tall. You enter the numbers, pick the DuBois formula, and boom—BSA is about 1.84 m². If a medicine calls for 100 mg per m², that means the correct dose is 184 mg. Much easier than pulling out a calculator and hoping you didn’t mess up a decimal.

Button-Pressing Made Easy

Using the BSA Calculator is simple. Just follow these steps:

Pick your measurement system: Metric or Imperial.
Type in your height and weight.
Choose the formula you want to use (DuBois is the most common).
Hit the "Calculate BSA" button.
Boom! Your BSA appears along with a chart, comparison, and helpful examples.
Want to start fresh? Tap "Reset" and enter new numbers.

No tricks. No tough math. Just clear, fast answers.

The Final Equation

Whether you’re studying, helping someone, or just curious, the BSA Calculator makes health math easier. It’s not just a number—it helps with real things like medicine doses and health planning.

And hey, even if you're not in the mood for debunking medical textbooks or embracing a new side of science, it's nice to know you’ve got a tool that’s always ready when you are.

Think of it like your calculator buddy—chill, accurate, and never too busy to help.