Body Mass Index (BMI) For All Nursing Exams, Check Purpose, Formulas & Importance
Body Mass Index (BMI) is a key nursing exam topic used to assess body weight and nutritional status. Calculated using weight and height, BMI categories range from underweight to obesity Class III. It helps identify health risks and supports diet planning, patient care, and exam preparation.
Aarti .7 Feb, 2026
Share
Body Mass Index, commonly known as BMI, is an important topic for nursing examinations. It is frequently asked in objective questions, short notes, and case-based problems. Nursing students must clearly understand the meaning, calculation, and classification. BMI is also useful in clinical practice. It helps nurses assess the nutritional status of patients.
What is Body Mass Index (BMI)
BMI stands for Body Mass Index. It is a numerical value. It is calculated using a person’s weight and height.
BMI is used to assess body fat. It helps to identify whether a person is underweight, normal weight, overweight, or obese.
BMI is mainly used for adults. It applies to both men and women. The same formula can be used for children. However, it is less commonly used for children in exams.
Key Facts for Exams:
-
Primary Goal: To evaluate nutritional status and health risks.
-
Standard Unit: Kilograms per meter squared (kg/m2).
-
Authority: Guidelines are set by the WHO (World Health Organization).
Purpose of Body Mass Index (BMI)
The main purpose of BMI is to assess nutritional status. It helps health professionals understand body weight status. BMI helps to:
-
Identify undernutrition
-
Detect overweight conditions
-
Classify obesity
-
Assess health risk related to body weight
In nursing practice, BMI is used during patient assessment. It supports the planning of diet and care. For exams, BMI helps test basic health assessment knowledge.
BMI Calculation Formulas
Nursing exams often require you to calculate BMI using two different systems. You must memorize both formulas.
1. The Metric System
This is the most common method used in hospitals and global exams.
-
Note: If height is given in centimeters, divide by 100 to convert it to meters before squaring it.
2. The Imperial System
This method uses pounds and inches. It is common in specific regions like the United States.
-
Tip: Remember that 1 foot equals 12 inches.
Official BMI Categories
The WHO classifies BMI into specific ranges. Nursing students must memorize these categories for accurate patient assessment.
|
Official BMI Categories |
||
|
BMI Range (kg/m2) |
Category |
Health Status |
|
Below 18.5 |
Underweight |
Nutritional deficit |
|
18.5 – 24.9 |
Normal weight |
Healthy range |
|
25.0 – 29.9 |
Overweight |
Pre-obesity |
|
30.0 – 34.9 |
Obesity Class I |
Moderate risk |
|
35.0 – 39.9 |
Obesity Class II |
Severe risk |
|
40.0 and above |
Obesity Class III |
Very severe risk |
Clinical Importance of BMI
As a nurse, you must understand why BMI matters for patient outcomes. High BMI levels are linked to several chronic health conditions:
-
Cardiovascular Disease: Higher risk of coronary artery disease and hypertension.
-
Metabolic Disorders: Increased incidence of Type 2 Diabetes Mellitus.
-
Musculoskeletal Issues: Stress on joints leading to osteoarthritis.
-
Mortality: Obesity is a leading cause of preventable death worldwide.
Nursing Tip: While BMI is a useful screening tool, it does not directly measure body fat percentage. It may be less accurate for athletes with high muscle mass or elderly patients with low muscle mass.
Body Mass Index is a basic and important topic for nursing exams. It helps assess body weight and nutritional status. BMI is simple to calculate and easy to understand.
Nursing students must know the definition, formula, unit, and categories of BMI. They must also understand its health significance. A clear understanding of BMI improves exam performance. It also supports better patient care in nursing practice.