Formula to calculate BMI is?

Appeared in: AIIMS Patna NO - 2020

Explanation

The correct formula for Body Mass Index (BMI) is Weight in kilograms (kg) divided by the square of the height in meters (m²).
This is the universally accepted formula, also known as Quetelet's index, used by the World Health Organization (WHO) for assessing nutritional status in adults.
The units must be metric (kilograms for weight and meters for height) for the standard calculation to be accurate.
For example, a person weighing 70 kg with a height of 1.75 m has a BMI of 22.9 (70 / (1.75 * 1.75)), which falls into the normal weight category.

Option B: This option is incorrect because it uses height in feet and does not square the height. Both the unit of measurement and the mathematical operation are wrong for the standard BMI formula.
Option C: This option is incorrect because it uses height in feet. Although it correctly squares the height value, the standard BMI formula requires height to be measured in meters.
Option D: This option is incorrect because it does not square the height measurement. This would result in a simple weight-to-height ratio, not the Body Mass Index.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Calculation and interpretation of Body Mass Index (BMI) as background academic context rather than a clinical decision trigger.
Nurses use BMI as a quick, non-invasive screening tool to identify patients who may be at risk for health problems due to being underweight, overweight, or obese.
A high BMI is a significant risk factor for non-communicable diseases like type 2 diabetes, cardiovascular disease, hypertension, and certain cancers, guiding patient education and lifestyle counseling.
In the Indian context, there is a rising trend of overweight and obesity, especially in urban areas. Nurses play a crucial role in community health screenings using BMI to tackle this public health issue.

How to Approach the Question

First, identify the core of the question, which asks for the 'formula' to 'calculate BMI'.
Recall the standard definition of BMI. The key components are 'weight', 'height', and the specific 'units' and 'mathematical operations' involved.
Evaluate each option against the standard formula. The correct formula uses kilograms for weight and meters for height, and the height value is squared.
Eliminate options that use incorrect units (like feet) or incorrect mathematical operations (like not squaring the height).
Confirm your choice: Weight (kg) / Height (m)². This matches the first option.

Concept Tested & Keywords

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E6 Parks TextBook of Preventive & Social Medicine part 1 — Subpart C (pp 404-604 of 604) p. 69-71

E6 Nursing Fundamentals Potter Perry 12e Part 5 p. 190-192

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