Frequently asked questions
Straight answers about BMI, its limitations, and how to read your result.
What is BMI?
Body Mass Index (BMI) is a screening number calculated from your weight and height. It gives a general sense of whether your weight falls within a typical range for your height — it isn't a measurement of body fat or a diagnosis.
How is BMI calculated?
For adults, BMI = weight in kilograms ÷ (height in metres)². If you use pounds and inches, the calculator converts these automatically before applying the same formula.
What is a healthy BMI?
For most adults, a BMI between 18.5 and 24.9 is categorized as "normal weight." This range is a population-level reference, not a guarantee of individual health.
Is BMI accurate for everyone?
No single number can capture everyone's health. BMI can be less informative for very muscular people, older adults, pregnant people, and certain ethnic groups, among others. It's a starting point, not a final answer.
Does BMI measure body fat?
No. BMI is a ratio of weight to height. It does not directly measure body fat percentage or where fat is distributed on the body.
Does BMI work for children?
Not in the same way as adults. Children and teenagers are generally assessed using age- and sex-specific BMI percentiles compared to growth charts, because healthy body composition changes as kids grow. A pediatrician is the right resource for interpreting a child's BMI.
Can athletes have a high BMI?
Yes. Because BMI can't distinguish muscle from fat, athletes and other muscular individuals sometimes fall into "overweight" or "obesity" categories despite having low body fat.
How often should I calculate my BMI?
There's no universal schedule. Some people check occasionally alongside other health markers. BMI is more useful as one data point over time than as a single snapshot.
What is the difference between BMI and body fat percentage?
BMI compares weight to height using a simple formula. Body fat percentage estimates how much of your body mass is fat tissue, typically using methods like skinfold calipers, bioelectrical impedance, or DEXA scans. They measure different things and can disagree for the same person.
What is a healthy weight range?
It's an estimated weight span produced by applying the standard adult BMI boundaries (18.5 and 24.9) to your height. It's a mathematical estimate rather than a personalized medical recommendation.