BMI Explained: What Your Number Really Means

Body Mass Index (BMI) is one of the most widely used health screening tools. It provides a quick estimate of whether your weight falls within a healthy range for your height.

How BMI Is Calculated

BMI equals weight in kilograms divided by height in meters squared. In imperial units, multiply weight in pounds by 703, then divide by height in inches squared. Use our BMI Calculator for instant results.

BMI Categories

Underweight is below 18.5. Normal weight ranges from 18.5 to 24.9. Overweight is 25 to 29.9. Obese is 30 and above. These categories were established by the World Health Organization.

Limitations of BMI

BMI does not distinguish between muscle and fat. A muscular athlete may have a high BMI despite being very healthy. It also does not account for age, sex, ethnicity, or body composition. Waist circumference and body fat percentage are complementary measures.

When BMI Is Useful

BMI works well as a population-level screening tool and for tracking individual weight changes over time. It correlates with health outcomes for most people and requires no special equipment.

Beyond the Number

Focus on overall health markers rather than BMI alone. Regular exercise, balanced nutrition, adequate sleep, and stress management matter more than any single number. Our Body Fat Calculator and Calorie Calculator provide additional insights.