BMI Calculator

Find your BMI and healthy weight range.

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Info only. Not medical advice.

About BMI

Body Mass Index (BMI) is a simple calculation using a person's height and weight. The formula is BMI = kg/m² where kg is a person's weight in kilograms and m² is their height in meters squared.

BMI Categories for Adults:

Underweight: BMI less than 18.5
Normal weight: BMI 18.5 to 24.9
Overweight: BMI 25 to 29.9
Obesity: BMI 30 or greater

For Children and Teens (2-19 years):

BMI is calculated the same way, but the interpretation is different. Results are compared to typical values for other children of the same age and sex, using percentiles:

Underweight: Less than the 5th percentile
Healthy weight: 5th to 84th percentile
Overweight: 85th to 94th percentile
Obesity: 95th percentile or greater

Limitations of BMI:

BMI is a useful screening tool, but it has limitations. It doesn't distinguish between muscle and fat, nor does it account for factors like age, sex, ethnicity, or muscle mass. Athletes and muscular individuals may have a high BMI without excess fat.

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Frequently Asked Questions About BMI

For adults, a healthy BMI typically ranges from 18.5 to 24.9 according to WHO standards. BMI under 18.5 is considered underweight, 25.0–29.9 is overweight, and 30.0 or higher is obese. BMI is a useful screening tool, but it doesn't distinguish muscle from fat and should be interpreted alongside other health markers.

BMI is helpful for population screening but has limitations. It may misclassify athletes with high muscle mass, and it doesn't account for fat distribution or differences by age and ethnicity. Consider pairing BMI with waist measurements or body fat percentage.

BMI = weight (kg) / height² (m²). For imperial units: (weight in pounds / height in inches²) × 703. Example: (150 / 65²) × 703 = 24.9.

Yes. Some people have a normal BMI but higher visceral fat or low muscle mass. Waist circumference, body fat percentage, and metabolic markers (blood pressure, glucose, lipids) provide more context.

Learn more about BMI

Understanding Your BMI

BMI provides a simple numeric measure of your weight relative to height. It was developed in the 19th century by Belgian mathematician Adolphe Quetelet and is widely used as a screening tool to categorize weight status.

Why BMI Matters

Research has shown that BMI correlates with direct measures of body fat and with various health risks. Higher BMIs are associated with increased risk for conditions like:

Heart disease and stroke
Type 2 diabetes
High blood pressure
Certain types of cancer
Sleep apnea and breathing problems
Osteoarthritis

Beyond BMI

While BMI is useful for population studies and general screening, it doesn't tell the complete story about your health. Other factors to consider include:

Body composition: The ratio of fat to muscle in your body
Fat distribution: Where fat is stored on your body (abdominal fat carries higher health risks)
Waist circumference: A measurement of abdominal fat
Lifestyle factors: Diet quality, physical activity, sleep, and stress
Family history: Genetic predisposition to certain conditions

For a more comprehensive assessment of your health status, consider using our other calculators like the Body Fat Calculator or ABSI Calculator, and consult with healthcare professionals.

Body Composition