BMI Calculator

A healthy BMI range is between 18.5 and 24.9. This indicates a weight considered healthy for your height according to WHO and CDC standards. A BMI below 18.5 is classified as underweight, 25–29.9 as overweight, and 30 or above as obese.

BMI is a useful screening tool but does not distinguish between muscle and fat mass. Athletes with high muscle mass may have a high BMI without excess body fat. It also does not account for bone density, age, sex, or ethnicity — so it should be used as one of several indicators, not a standalone diagnosis.

Underweight: below 18.5 — may indicate malnutrition or other health concerns. Normal weight: 18.5–24.9 — associated with lowest health risk. Overweight: 25–29.9 — increased risk for cardiovascular disease. Obese Class I: 30–34.9, Class II: 35–39.9, Class III: 40+ — progressively higher risk for diabetes, heart disease, and other conditions.

BMI is calculated by dividing your weight in kilograms by your height in meters squared. The formula is BMI = kg / m². For example, a person weighing 70 kg and standing 1.75 meters tall has a BMI of 70 / (1.75 × 1.75) = 22.9, which falls in the normal weight range. If you use imperial units, the formula is (weight in pounds / (height in inches)²) × 703. Understanding this formula helps you verify the calculator's result and see how small changes in weight or height affect your BMI score.

Smart scales often use bioelectrical impedance analysis (BIA) to estimate body fat percentage, then derive a BMI-like number that may incorporate additional factors. The BMI calculator on this site uses the standard WHO formula based solely on height and weight. If you want a more comprehensive body composition analysis, consider combining BMI with waist circumference measurements, body fat percentage, and fitness level. BMI is best used as a starting point for health discussions with your doctor, not as a definitive measure of your overall health.