BMI Calculator
Free online BMI calculator to check if you have a healthy weight. Calculate your Body Mass Index (BMI) based on height and weight and find your BMI category.
Body Mass Index (BMI) is a simple calculation based on your height and weight that gives an indication of whether you're underweight, a healthy weight, overweight, or obese. This BMI calculator provides results using both metric (kg, cm) and imperial (lb, in) units.
How This Tool Works
The Body Mass Index (BMI) is calculated by dividing your weight by the square of your height. The formula differs slightly depending on the units used:
- Metric: BMI = weight(kg) / (height(m))²
- Imperial: BMI = 703 × weight(lb) / (height(in))²
Once calculated, your BMI falls into one of these categories:
- Underweight: BMI less than 18.5
- Normal weight: BMI between 18.5 and 24.9
- Overweight: BMI between 25 and 29.9
- Obesity: BMI 30 or greater
Frequently Asked Questions
Is BMI an accurate measure of health?
BMI is a useful screening tool, but it's not a diagnostic of body fatness or health. BMI doesn't directly measure body fat and doesn't account for factors like muscle mass, bone density, or overall body composition. Athletes with high muscle mass may have a high BMI without excess fat. Always consult healthcare professionals for a complete health assessment.
Why do the BMI categories exist?
BMI categories were developed based on statistical associations between BMI ranges and health outcomes in large population studies. They provide guidelines for identifying potential weight-related health risks. The categories help healthcare providers assess whether a person might be at an increased risk for certain health conditions associated with weight.
Are there different BMI calculators for children and adults?
Yes, BMI is calculated differently for children and teenagers. For children and teens (aged 2-20), BMI is calculated the same way as for adults, but the results are interpreted differently. Instead of fixed categories, children's BMI results are compared to percentiles based on age and sex, often referred to as "BMI-for-age." This calculator is intended for adult use only.
Tips and Best Practices
Tips for using the BMI calculator and interpreting results:
- For the most accurate results, measure your height without shoes and weight in the morning before eating.
- BMI doesn't differentiate between fat and muscle. If you're athletic with significant muscle mass, BMI may overestimate your body fat.
- BMI doesn't account for where fat is stored. Abdominal fat (around the waist) may indicate higher health risks than fat in other areas.
- Consider using BMI alongside other measurements like waist circumference or body fat percentage for a more complete assessment.
- If your BMI falls outside the "normal" range, consult with a healthcare professional before making significant lifestyle changes.