Author
BetterProduct Editorial Team
Body Mass Index (BMI) is one of the most widely used health screening tools in the world, yet it's also one of the most misunderstood. BMI provides a quick estimate of whether your weight is in a healthy range for your height, but it has significant limitations. Understanding what BMI measures — and what it doesn't — helps you use it as one tool among many for assessing your health.
BetterProduct Editorial Team
Checked against public health guidance and standard screening formulas. Not a diagnosis.
March 2026
Educational estimates and everyday wellness planning.
7 language editions aligned from the same source formulas.
BMI is calculated by dividing your weight in kilograms by the square of your height in meters: BMI = kg/m². In imperial units: BMI = (weight in lbs × 703) / (height in inches)². For adults, the standard categories are: under 18.5 (underweight), 18.5–24.9 (normal), 25–29.9 (overweight), and 30+ (obese).
BMI doesn't distinguish between muscle and fat — a muscular athlete may have a high BMI while being very lean. It doesn't account for fat distribution (belly fat is more dangerous than hip fat). BMI thresholds were developed primarily from studies of white European populations and may not be accurate for other ethnic groups. It also doesn't reflect age-related changes in body composition.
Waist circumference is a better predictor of metabolic risk than BMI — men should aim for under 40 inches, women under 35 inches. Waist-to-height ratio (waist should be less than half your height) is another useful metric. Body fat percentage measured by DEXA scan, hydrostatic weighing, or bioelectrical impedance provides the most accurate picture.
Rather than focusing solely on BMI, aim for sustainable healthy habits: regular physical activity (150+ minutes/week), a balanced diet rich in whole foods, adequate sleep, and stress management. Small, consistent improvements in these areas improve health outcomes regardless of what the scale says.