Calculate your BMI and find out whether you are underweight, normal weight, overweight, or obese using the WHO classification.
How BMI Is Calculated
Body Mass Index divides weight in kilograms by height in metres squared (BMI = kg / m²). It produces a single number used to screen for underweight, normal weight, overweight, and obesity ranges across a population, using the World Health Organization's standard cut-offs: underweight below 18.5, normal weight 18.5–24.9, overweight 25–29.9, and obese 30 and above.
What BMI Doesn't Measure
BMI cannot distinguish muscle mass from fat mass, so a muscular athlete can register as "overweight" despite having low body fat, while someone with low muscle mass and high body fat can register as "normal weight." It also doesn't account for where fat is distributed, age, or bone density, all of which affect actual health risk more precisely than the BMI number alone.
What to Do With Your Result
BMI is a screening tool, not a diagnosis. Use it as a starting point for a conversation with a healthcare provider, who can combine it with waist circumference, body composition, and other factors for a fuller picture of health risk.
What is a healthy BMI range?
The WHO classifies a BMI of 18.5–24.9 as normal weight. Below 18.5 is underweight, 25–29.9 is overweight, and 30 or above is obese.
Is BMI accurate for athletes?
BMI can overstate health risk for muscular athletes, since it cannot distinguish muscle mass from fat mass — a person with high muscle mass and low body fat can register as overweight despite low actual health risk.