Compyrix logo

BMI Calculator

Calculate your Body Mass Index in metric or imperial units.

Body Mass Index (BMI) is a widely used screening tool that categorizes adults into weight groups based on their height and weight. Our free BMI Calculator supports both metric (kg, cm) and imperial (lb, ft/in) unit systems and provides instant results with your BMI category and healthy weight range.

To calculate your BMI, select your preferred unit system, enter your height, and enter your weight. The result shows your BMI value, a colored indicator showing where you fall on the BMI scale (Underweight, Normal, Overweight, Obese), and the healthy weight range for your height.

BMI is calculated as weight in kilograms divided by height in meters squared (kg/m²). For imperial units, we use the conversion factor 703 multiplied by weight in pounds divided by height in inches squared. Both methods produce identical results.

Important: BMI is a screening tool, not a diagnostic measure. It does not distinguish between muscle and fat mass, so athletes and bodybuilders may have a high BMI without excess body fat. It also does not account for age, gender, bone density, or body fat distribution. For personalized health advice, consult a qualified healthcare provider.

Frequently Asked Questions

What is a healthy BMI range?
According to the World Health Organization (WHO) and CDC, a normal/healthy BMI for adults is 18.5 to 24.9. Below 18.5 is underweight, 25.0 to 29.9 is overweight, and 30.0+ is obese. Ideal ranges may vary slightly by ethnicity and age.
Is BMI accurate for everyone?
BMI works best for most adults between ages 18 and 65. It may be less accurate for pregnant women, competitive athletes with high muscle mass, the elderly who have lost muscle mass, and children (who use age-and-gender-specific BMI percentiles instead).
Why does the calculator show a "healthy weight range"?
The healthy weight range shows the minimum and maximum weight that would fall within the normal BMI category (18.5–24.9) for your height. This gives you a target range rather than a single number, which is more realistic and sustainable.
Should I use BMI to decide if I need to lose weight?
BMI is a starting point, not a final answer. Consider other factors like waist circumference, blood pressure, cholesterol, blood sugar, energy levels, and family history. A holistic assessment with your doctor is the best way to determine your ideal weight.

Related Tools