Body Surface Area Calculator

What is a body surface area calculator?

A body surface area calculator estimates the total external surface area of your body in square metres (m²) from just your height and weight. Body surface area, or BSA, is a single figure that scales with overall body size. The tool above takes two simple inputs and returns your BSA to two decimal places, instantly and in your browser.

BSA matters because some clinical and physiology calculations track body surface area more closely than they track weight alone. It is a quick reference number used in certain medication dosing protocols, in describing cardiac output relative to size, and in research that needs a fair way to compare people of different builds. For most adults the result lands somewhere between 1.5 and 2.0 m².

How does the BSA calculator work?

This calculator uses the Mosteller formula, the most common BSA equation in everyday clinical use because it is easy to compute and reliable for typical adults:

BSA (m²) = √(height_cm × weight_kg ÷ 3600)

In plain terms, multiply your height in centimetres by your weight in kilograms, divide by 3600, then take the square root. The terms are:

• height_cm — standing height in centimetres.
• weight_kg — body mass in kilograms.
• 3600 — a fixed constant built into the Mosteller formula (it has no separate unit you enter).
• √ — the square root, which converts the product back into a length-squared (area) value, giving m².

If you enter imperial units, the tool converts first: inches are multiplied by 2.54 to get centimetres, and pounds are multiplied by 0.45359237 to get kilograms. The converted figures are then fed into the same Mosteller formula, and the result is rounded to two decimals.

Examples

Here are fully worked calculations that match the tool’s output exactly.

Example 1 — 175 cm, 70 kg

• Multiply: 175 × 70 = 12,250
• Divide: 12,250 ÷ 3600 = 3.403
• Square root: √3.403 = 1.84 m²

Example 2 — 160 cm, 60 kg

• Multiply: 160 × 60 = 9,600
• Divide: 9,600 ÷ 3600 = 2.667
• Square root: √2.667 = 1.63 m²

Example 3 — 69 in, 154 lb (imperial)

• Convert: 69 × 2.54 = 175.26 cm; 154 × 0.45359237 = 69.85 kg
• Multiply: 175.26 × 69.85 = 12,242
• Divide and root: √(12,242 ÷ 3600) = √3.401 = 1.84 m²

Notice that Example 3 lands on the same 1.84 m² as Example 1, because 69 in and 154 lb convert to almost exactly 175 cm and 70 kg.

BSA reference table (Mosteller formula)

The table below shows BSA in m² calculated straight from the Mosteller formula across a grid of heights and weights. Find the row nearest your height and the column nearest your weight for a quick estimate.

Height	50 kg	60 kg	70 kg	80 kg	90 kg
150 cm	1.44	1.58	1.71	1.83	1.94
160 cm	1.49	1.63	1.76	1.89	2.00
170 cm	1.54	1.68	1.82	1.94	2.06
180 cm	1.58	1.73	1.87	2.00	2.12
190 cm	1.62	1.78	1.92	2.05	2.18

Two patterns are clear: BSA rises with both height and weight, but because the formula uses a square root, it grows more gently than weight does. Doubling weight does not double surface area. For a precise figure, enter your exact numbers in the tool above.

Common uses

A BSA figure shows up in several places:

• Medication dosing. Some drugs, including a number used in chemotherapy, are prescribed in milligrams per square metre, so BSA is calculated first by the prescribing clinician.
• Cardiac and renal indices. Measures such as cardiac index express output per square metre of body surface, allowing fair comparison between people of different sizes.
• Physiology and research. Scaling values like metabolic rate or fluid needs to surface area gives a more even basis for comparison than weight alone.
• Quick self-reference. Comparing your BSA against a typical adult range of roughly 1.5 to 2.0 m² gives a sense of overall body size.

Tips and common mistakes

• Use centimetres, not metres. The Mosteller formula expects height in cm (e.g. 175, not 1.75). The imperial mode handles the conversion for you.
• Match your units. Do not mix inches with kilograms; pick metric or imperial and keep both inputs in that system.
• Pick the right formula. Mosteller is the standard here, but other equations (Du Bois, Haycock, Gehan-George) exist and give slightly different numbers; do not compare a Mosteller result against another formula’s figure.
• Treat it as an estimate. A BSA of 1.84 m² is a calculated approximation of body size, not a measured area of skin.
• Do not self-dose. Even if a label lists a dose per m², calculating your own BSA is not a basis for adjusting any medication yourself.

Limitations and notes

The Mosteller formula is simple and well validated for typical adults, but every BSA formula is a statistical estimate, not a direct measurement of your skin’s area. It depends only on height and weight, so two people with the same numbers receive the identical result regardless of build, body composition or fat distribution. It can be less reliable at the extremes — very tall, very short, very lean or higher-body-fat individuals — and it is not designed for the special considerations of infants, pregnancy or particular medical conditions, where clinicians may choose a different equation.

Health disclaimer: This body surface area calculator is provided for general information and education only. It is not medical advice and is not a substitute for professional clinical judgement. Any decision about medication dosing or your health must be made by a qualified healthcare professional.

For more health self-checks, try the BMI calculator to gauge weight for height, the BMR calculator for resting calorie burn, or the ideal weight calculator for a target weight range, and browse the full health & medical category for more tools.