BMI Calculator
Enter your values below and click Calculate for instant results.
ft
in
lbs
Calculate your Body Mass Index instantly from height and weight. Supports both imperial and metric units. Shows your BMI category and healthy range.
Enter your values below and click Calculate for instant results.
Body mass index (BMI) is a number calculated from height and weight that provides a general indicator of whether a person's weight falls within a healthy range for their height. It is one of the most widely used screening tools in healthcare because it is simple, free, and reasonably correlated with body fat at the population level.
BMI is a screening tool, not a diagnostic one. A person with a high BMI may have a perfectly healthy body composition, and a person with a normal BMI may have health risks that BMI does not capture. Athletes with significant muscle mass often register as overweight by BMI despite being in excellent health.
The World Health Organization defines BMI categories as follows for adults: underweight is below 18.5, normal weight is 18.5 to 24.9, overweight is 25 to 29.9, and obese is 30 and above. These thresholds apply to adults 20 and older. For children and teenagers, BMI is interpreted differently using age and sex-specific percentile charts.
BMI does not distinguish between muscle and fat, so muscular individuals often show higher BMIs than their body composition warrants. It also does not account for where fat is distributed on the body. Abdominal fat carries higher health risks than fat distributed elsewhere, and BMI does not capture this distinction. Age matters too, since older adults tend to have more body fat at the same BMI compared to younger adults.
In metric units, BMI equals weight in kilograms divided by height in meters squared. In imperial units, the formula is weight in pounds divided by height in inches squared, multiplied by 703. This calculator handles both unit systems and returns the same result either way.