BMI Calculator

How BMI Is Calculated

What Is BMI?

BMI (Body Mass Index) is a numerical value derived from your weight and height. It provides a simple screening metric to categorize individuals as underweight, normal weight, overweight, or obese based on World Health Organization standards. While it doesn't directly measure body fat, it correlates moderately with more direct measures like skinfold thickness and bioelectrical impedance.

How Is BMI Calculated?

BMI is calculated by dividing your weight in kilograms by the square of your height in meters. For imperial units, the formula is: BMI = (weight in pounds × 703) / (height in inches)². For example, a person weighing 70 kg who is 1.75 m tall has a BMI of 70 / (1.75 × 1.75) = 22.9, placing them in the "Normal weight" range.

BMI Categories (WHO Classification)

• Underweight: BMI below 18.5 — may indicate malnutrition or underlying health conditions.
• Normal weight: BMI 18.5–24.9 — associated with the lowest health risks.
• Overweight: BMI 25.0–29.9 — increased risk of cardiovascular disease and diabetes.
• Obese: BMI 30.0 and above — significantly elevated health risks.

Limitations of BMI

BMI is a screening tool, not a diagnostic instrument. It doesn't account for muscle mass, bone density, or body composition — athletes with high muscle mass may classify as "overweight" despite having low body fat. For a comprehensive health assessment, combine your BMI with your TDEE, body fat percentage, and waist circumference measurements.