BMI, or Body Mass Index, is a measure of body fat based on a person’s weight in relation to their height. It is calculated by dividing a person’s weight (in kilograms) by the square of their height (in meters).

How is BMI calculated?

BMI is calculated using two systems: Metric (kg/m²) and Imperial (lbs/in² × 703). In the metric system, BMI is calculated by dividing weight (kg) by height (m) squared. In the imperial system, it’s calculated by dividing weight (lbs) by height (in) squared and then multiplying by 703.

What does BMI indicate?

BMI provides an indication of whether a person is underweight, normal weight, overweight, or obese. It is used as a screening tool to assess potential health risks, although it does not directly measure body fat.

What are the BMI categories?

The World Health Organization (WHO) defines the following BMI categories: - Less than 16: Severe underweight - 16 – 18.5: Underweight - 18.5 – 25: Normal weight - 25 – 30: Overweight (Pre-obesity) - 30 – 35: Obesity Class I - 35 – 40: Obesity Class II - 40 and more: Obesity Class III (Morbid)

Best BMI Calculator Online

Calculate your Body Mass Index (BMI) with our best BMI Calculator. Supports metric and imperial units, including WHO classification.

🌟 BMI Calculator

Metric (kg/cm) Imperial (lbs/in)

Weight kg Height cm

BMI Range	Classification (WHO)
Less than 16	Severe underweight
16 – 18.5	Underweight
18.5 – 25	Normal weight
25 – 30	Overweight (Pre-obesity)
30 – 35	Obesity Class I
35 – 40	Obesity Class II
40 and more	Obesity Class III (Morbid)

How to Calculate BMI with BMI Calculator

Medical Definition

Body Mass Index (BMI) is a standardized, non-invasive anthropometric measurement used to assess an individual’s body weight relative to height. It is calculated using a mathematical formula and serves as a quick screening tool to classify underweight, normal weight, overweight, and obesity in adults.

BMI is widely used in clinical settings because it correlates moderately well with body fat percentage in most individuals, though it does not directly measure fat distribution or lean mass.

BMI Calculation Examples with Real-World Cases

Example 1: Metric Calculation (kg/m²)

Patient: Female, Age 28

Height: 1.65 meters

Weight: 68 kilograms

Calculation:

BMI = Weight (kg) / [Height (m)]²
BMI = 68 / (1.65 × 1.65)
BMI = 68 / 2.7225
BMI = 24.97

Interpretation:

A BMI of 24.97 falls within the “Normal” category (18.5–24.9) according to the WHO classification. This indicates a healthy body weight for this patient.

Example 2: Imperial Calculation (lbs/in² × 703)

Patient: Male, Age 35

Height: 5 feet 10 inches = 70 inches

Weight: 210 pounds

Calculation:

BMI = (Weight (lb) / [Height (in)]²) × 703
BMI = (210 / (70 × 70)) × 703
BMI = (210 / 4900) × 703
BMI = 0.042857 × 703
BMI = 30.14

Interpretation:

A BMI of 30.14 places the individual in Obese Class I. Clinical intervention is advisable, including lifestyle modification and possibly further metabolic screening.

Our Best Calculators

Stock Average Calculator

Gratuity Calculator

Important Considerations

BMI is not diagnostic: It should be used alongside other indicators like waist circumference, body composition analysis (e.g., DEXA), lipid profile, and fasting glucose levels.
Athletes and muscular individuals may have a high BMI due to lean mass, not excess fat.
Older adults may have a normal BMI but increased visceral fat and sarcopenia (loss of muscle mass).
Pediatric patients: Use BMI-for-age percentiles from the CDC or WHO growth charts instead of adult ranges.

FAQs

BMI (Body Mass Index) is a widely used tool for assessing whether a person has a healthy body weight relative to their height. It helps identify individuals who are underweight, at a normal weight, overweight, or obese. While BMI doesn’t directly measure body fat, it provides a reliable estimate of potential health risks. A BMI in the “normal” range (18.5–24.9) is associated with a lower risk of chronic conditions such as cardiovascular disease, diabetes, and certain cancers. BMI values outside this range indicate potential health risks that require medical attention.

BMI is an excellent screening tool for identifying individuals who may be at risk for certain health conditions. However, it has limitations as it does not differentiate between muscle and fat. For example, athletes with high muscle mass may have a higher BMI but not have excess body fat. Similarly, older adults may have a normal BMI but higher body fat percentage. Therefore, BMI should be considered alongside other clinical assessments, such as body fat percentage measurements, waist circumference, and other health screenings, for a more accurate evaluation of health risks.

A BMI greater than 30 falls into the “obese” category, which is linked to various health risks, including:

Type 2 diabetes
Hypertension (high blood pressure)
Cardiovascular diseases (heart disease, stroke)
Sleep apnea
Certain cancers (breast, colon, kidney, liver, etc.)
Osteoarthritis (joint issues)

Obesity also increases the risk of mental health issues such as depression and anxiety. If you fall within this category, it is advisable to consult a healthcare provider for a comprehensive evaluation and to discuss lifestyle modifications, such as diet and exercise.

If your BMI falls outside the normal range (either underweight or overweight), it is essential to take action to improve your health. For those who are overweight or obese, a combination of a balanced diet and regular physical activity is key to achieving a healthy weight. The CDC recommends at least 150 minutes of moderate-intensity physical activity per week. Consulting with a healthcare provider or a registered dietitian for personalized advice on nutrition and exercise is crucial for developing a sustainable and safe weight management plan. Additionally, if you’re underweight, focusing on nutrient-dense foods and increasing caloric intake can help bring your BMI into a healthier range.

Best BMI Calculator Online

🌟 BMI Calculator