Calculate your Body Mass Index instantly. Understand your weight category and take steps toward a healthier life.
Body Mass Index (BMI) is a simple numerical measure of a person's body fat based on their weight and height. It is widely used by doctors, dietitians, and health professionals as a quick screening tool to identify potential weight problems in adults. While BMI does not directly measure body fat, it correlates well with direct measures of body fat and can indicate health risks.
Developed by Belgian mathematician Adolphe Quetelet in the 19th century, BMI has become the most widely accepted international standard for assessing healthy body weight relative to height. Organizations like the World Health Organization (WHO) and the Centers for Disease Control (CDC) use BMI classifications to monitor population health.
The BMI formula is straightforward:
For example, if you weigh 70 kg and are 175 cm (1.75 m) tall: BMI = 70 ÷ (1.75)² = 70 ÷ 3.0625 = 22.86 — which falls in the Normal range.
While BMI is a useful population-level screening tool, it has some limitations for individuals:
Always consult a healthcare professional for a comprehensive health assessment. BMI is one of many tools, not a definitive diagnosis.
If your BMI is outside the normal range, lifestyle changes can help:
For adults (20 years and older), a BMI between 18.5 and 24.9 is considered healthy or "normal" by the World Health Organization. However, what's healthy can vary slightly based on age, sex, and ethnicity. A BMI of 25–29.9 is considered overweight, and 30 or above is classified as obese.
BMI is a useful screening tool but has limitations. It may overestimate body fat in athletes and bodybuilders (who have more muscle mass) and underestimate it in elderly people (who may have lost muscle). For a more complete picture of health, consider waist circumference, body fat percentage, and other metrics.
No — this calculator uses the adult BMI formula. For children and teenagers (ages 2–19), BMI is calculated the same way but interpreted using age- and sex-specific percentile charts from the CDC or WHO. A pediatrician should evaluate BMI in children.
There's no strict rule, but most health professionals suggest checking your BMI every 3–6 months if you're actively working on weight management. For maintenance, an annual check during a routine health screening is usually sufficient.
If your BMI is 30 or above, it's advisable to consult a healthcare professional. They can assess additional risk factors (blood pressure, cholesterol, blood sugar) and recommend a safe, personalized plan involving dietary changes, physical activity, and possibly medical support.
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