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BMI and body surface area

Body mass index from weight and height, with Mosteller body surface area alongside it — the number a chemotherapy or paediatric dose is worked from.

An illustration of a clinic toolkit: calculators, checklists, guides and reports
Fill the fields above and the answer appears here, with the working spelled out — the same working the in-product version saves to the chart.
Nothing you type here is sent anywhere. The calculation runs in your browser and the page keeps no record of it.

How it is worked out

BMI = weight ÷ height². BSA uses Mosteller: √(height in cm × weight in kg ÷ 3600). The band is read against the Asian cut-offs the whole way up — under 18.5 underweight, 18.5–22.9 normal, 23–24.9 overweight, 25 and above obesity — which is the WHO Asia-Pacific and 2009 Indian consensus scale, not the international one where 25 is overweight and 30 is obesity.

What it does not do

BMI says nothing about where the weight sits, and it reads high in a muscular adult and low in an older one who has lost muscle. It is a screening number, not a diagnosis.

It is a calculator, not a clinician. Nothing here is medical advice, and the person prescribing owns the decision.

Save this to a patient’s chart

That is the one thing this page cannot do. Inside MedAppz the same calculator writes the value and its working onto the record, so a year later anybody reading the chart can see which numbers produced it. 15 more calculators come with it.

The other calculators