BMI Calculator – Body Mass Index Free Online

BMI (Body Mass Index) is a measure of body fat based on height and weight. The formula is: BMI = weight (kg) ÷ height² (m²). For imperial units: BMI = 703 × weight (lbs) ÷ height² (inches²). It is a widely used screening tool to categorize weight status in adults.

For adults aged 18 and above, a healthy BMI range is 18.5 to 24.9. A BMI below 18.5 is considered underweight, 25–29.9 is overweight, and 30 or above is classified as obese. These ranges may vary slightly for different ethnicities and age groups.

BMI is a useful general screening tool but has limitations. It does not directly measure body fat and may not accurately reflect health for athletes (who have high muscle mass), elderly individuals, pregnant women, or certain ethnic groups. Always consult a healthcare professional for a complete health assessment.

BMR (Basal Metabolic Rate) is the number of calories your body needs at complete rest to maintain basic functions like breathing and circulation. BMI measures weight relative to height for weight classification, while BMR tells you your minimum daily calorie requirement. Both are useful for health planning.

Simply select your unit system (Metric or Imperial), enter your gender, age, height, and weight, then click "Calculate BMI". The tool instantly shows your BMI, category, healthy weight range, ideal body weight, BMR, estimated body fat percentage, and personalized health tips.

Ideal body weight (IBW) is an estimate of the optimal weight for a given height. This calculator uses the Devine formula: For males — IBW = 50 kg + 2.3 kg per inch over 5 feet. For females — IBW = 45.5 kg + 2.3 kg per inch over 5 feet. It is a reference point, not an absolute target.

Yes! ToolNex BMI Calculator fully supports both Metric units (kilograms and centimeters) and Imperial units (pounds and feet/inches). Simply toggle between the two systems at the top of the calculator. All calculations are automatically adjusted for the selected unit system.