BMI (Body Mass Index) is a simple numerical measure calculated from a person's height and weight. It's widely used as a screening tool to identify potential weight categories that may lead to health problems. BMI is not a direct measure of body fat and doesn't account for muscle mass, bone density, age, or sex.
BMI is a useful but imperfect tool. It doesn't distinguish between muscle and fat — a very muscular person may have a high BMI but low body fat. It also doesn't account for where fat is distributed in the body. Doctors use BMI as a starting point, not a definitive health diagnosis. Other measures like waist circumference and body fat percentage provide additional context.
What is a healthy BMI for adults?
For most adults, a BMI between 18.5 and 24.9 is considered healthy. However, these ranges were originally developed using data primarily from white European populations. Research suggests the thresholds may differ for people of Asian descent, where health risks can appear at lower BMI values.
Does BMI apply to children?
Children's BMI is calculated the same way but interpreted differently — using age and sex-specific percentile charts rather than fixed thresholds. A pediatrician should interpret BMI results for children and teenagers. This calculator is intended for adults 18 and older.
What should I do if my BMI is outside the normal range?
BMI is a screening tool, not a diagnosis. If your BMI falls outside the 18.5–24.9 range, it's worth discussing with a healthcare provider. They can assess your overall health using a broader range of measures and provide personalized guidance. Small lifestyle changes — diet, physical activity, sleep — often have meaningful impacts over time.