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Body surface area calculator

Compute your body surface area (BSA) with the five published formulas — Mosteller, Du Bois, Haycock, Gehan & George and Boyd — side by side.

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Enter Weight (kg), Height (cm) and the Body surface area calculator works out Body surface area (m²), Du Bois (m²), Haycock (m²), Gehan & George (m²), Boyd (m²) straight away. For instance, with Weight (kg) = 70 and Height (cm) = 175 it returns Body surface area (m²) = 1.845, Du Bois (m²) = 1.848 and Haycock (m²) = 1.847.

How to use it

  1. Enter your values: Weight (kg), Height (cm).
  2. Read the result instantly: Body surface area (m²), Du Bois (m²), Haycock (m²), Gehan & George (m²), Boyd (m²).

Frequently asked questions

What does the Body surface area calculator actually compute?

It takes Weight (kg) and Height (cm) and derives Body surface area (m²), Du Bois (m²), Haycock (m²), Gehan & George (m²) and Boyd (m²) from them. The calculation is live as you type, so the result updates on every change.

What information do I need to provide?

2 values: Weight (kg) and Height (cm). Nothing else is required — no account, no file upload.

Can you show a worked example?

With Weight (kg) = 70 and Height (cm) = 175, the calculator returns Body surface area (m²) = 1.845, Du Bois (m²) = 1.848 and Haycock (m²) = 1.847. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

What happens if I enter larger values?

It moves a lot. Using Weight (kg) = 77 and Height (cm) = 193 instead, Body surface area (m²) goes from 1.845 to 2.032 — which is why it is worth testing a few scenarios rather than trusting a single figure.

What does it give for smaller values?

Scaled down to Weight (kg) = 63 and Height (cm) = 158, Body surface area (m²) comes out at 1.663. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Checking one clinical number against the definition that gives it meaning: a dose against a body weight, a laboratory value corrected for the albumin or glucose that distorted it, a blood pressure against a guideline's threshold table, a heart rate or a basal metabolic rate against the formula that defines it.

What is the most common mistake?

Reading the output as a finding. Every figure here is arithmetic on numbers you typed: a correction formula measures nothing, and a threshold table classifies one reading rather than a person. Blood pressure in particular means little until it has been measured repeatedly on separate occasions, and a dose worked out here is a way of checking a prescription, never of writing one.

How accurate is it, and what are the limits?

For general guidance only — not medical advice.

What is the difference between the Body surface area calculator and the Lean body mass calculator?

This one returns Body surface area (m²) and Du Bois (m²); the Lean body mass calculator returns Lean body mass (kg) and Fat mass (kg). That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Body fat calculator is the closest one after this: Estimate your body fat percentage (U.S. Navy method).

Further reading

All guides →
ExplainerWhat Is Body Surface Area (BSA)?Body surface area estimates your body's external area in square metres. Here is how it is calculated and why clinicians use it to dose medicines.ExplainerWhat Is Lean Body Mass? LBM vs Fat MassLean body mass is everything in your body that isn't fat. Learn how the Boer formula estimates it and why it matters for health and training.ExplainerBlood Donation Intervals, and What Your Body Is Actually ReplacingPlasma is back in a day, red cells in weeks, iron in months — and it is the iron that sets the interval. The arithmetic of a unit, and the minimum intervals published by seven national services.ExplainerHow Long Does Alcohol Stay in Your System?The body clears roughly one standard drink per hour. See how long alcohol stays in blood, breath and urine — and why you can't rush it.ExplainerWeight-Based Dosing, and Where the Arithmetic Goes WrongMilligrams per kilogram is one multiplication, and that is exactly why it fails: the documented errors are unit slips, misplaced decimal points and the wrong body weight, not hard maths. Here is the arithmetic done properly, the three body weights that give three different answers, and what body surface area changes.ExplainerWhat Is a Good Body Fat Percentage?Body fat percentage is a better health signal than weight alone. Here are the healthy ranges by sex, how it's measured, and how to use it wisely.