Free tool
BMI + BSA calculator
Enter height and weight to get Body Mass Index against both the WHO and the Asian-Indian risk bands, plus Body Surface Area by Mosteller and Du Bois. A screening reference — not a diagnosis.
WHO (universal)
Normal
Asian-Indian (consensus)
Overweight
A screening reference, not a diagnosis. BMI does not distinguish muscle from fat and is not validated for pregnancy, athletes, the very young, or the elderly. The Asian-Indian cut-offs are a widely-cited consensus (Misra et al. 2009 JAPI), not a single settled rule — clinical judgement decides. See the sources below. Runs entirely in your browser — no data is sent to any server.
Why two BMI bands
The BMI number is the same everywhere — weight in kilograms divided by height in metres squared. What changes is the line where risk is flagged. The international WHO band marks 25 as overweight and 30 as obese. For South Asians, a widely-cited consensus pulls those lines lower — overweight from 23, obese from 25 — because cardiometabolic risk tends to show up at a lower BMI. The same person can read normal on one scale and overweight on the other, which is exactly why this tool shows both.
Body Surface Area is used for dosing and physiology rather than weight status. We show two published estimates — Mosteller and Du Bois — which normally land within a few percent of each other. Both are screening references; neither replaces clinical assessment.
In the Avinya Plus chart, BMI is computed straight from the recorded height and weight on the vitals form, and every vital is shown against an age-aware reference range so an out-of-range value is obvious at a glance. This tool runs the same BMI math.
Frequently asked questions
- Why does this BMI calculator show two different bands?
- BMI is one number, but the cut-offs that flag risk differ by population. The WHO international band calls 25 overweight and 30 obese. A widely-cited Asian-Indian consensus uses lower cut-offs — overweight from 23 and obese from 25 — because cardiometabolic risk tends to appear at a lower BMI in South Asians. The tool shows both so you can see where a patient sits on each scale.
- What are the Asian-Indian BMI cut-offs?
- The commonly-used Asian-Indian consensus reads under 18.5 as underweight, 18.5 to under 23 as normal, 23 to under 25 as overweight, and 25 or above as obese. These are a widely-cited consensus, not a single settled regulatory rule, and clinical judgement still applies.
- How is body surface area calculated here?
- Two published formulas. Mosteller (1987) is the square root of height in cm times weight in kg, divided by 3600. Du Bois and Du Bois (1916) is 0.007184 times weight^0.425 times height^0.725. Both return square metres. They usually agree to within a few percent; this page cites both originals.
- Is BMI a diagnosis of obesity?
- No. BMI is a screening reference. It does not separate muscle from fat or account for fat distribution, and it is not validated for pregnancy, athletes, very young children, or the frail elderly. Use it alongside other measures and clinical assessment, not on its own.
- Where does the clinic software use BMI and these reference ranges?
- On the Avinya Plus vitals form, BMI is computed from the recorded height and weight, and each vital is shown against an age-aware reference range so an out-of-range value stands out at a glance. This free tool runs the same BMI math you would see in the chart.
Sources
- WHO Expert Consultation. Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies. Lancet. 2004;363(9403):157–163.
- Misra A, et al. Consensus statement for diagnosis of obesity, abdominal obesity and the metabolic syndrome for Asian Indians. J Assoc Physicians India. 2009;57:163–170.
- Mosteller RD. Simplified calculation of body-surface area. N Engl J Med. 1987;317(17):1098.
- Du Bois D, Du Bois EF. A formula to estimate the approximate surface area if height and weight be known. Arch Intern Med. 1916;17:863–871.
Reference bands and formulas are screening references, not a diagnosis, and not a substitute for clinical judgement. The Asian-Indian cut-offs are a widely-cited consensus, not a single settled regulatory rule.
BMI on the chart, the moment you record vitals.
In Avinya Plus, the vitals form computes BMI from the height and weight you enter and flags every vital against an age-aware reference range. See it on a live chart.