The BMI Calculator computes your Body Mass Index using the standard formula BMI = weight / height². It supports both metric (kg/cm) and imperial (lb/ft/in) units and classifies your result according to WHO categories.
Enter your weight and height to see your BMI, category classification, and healthy weight range. The gauge visualisation shows where you fall on the BMI scale.
Your calculations will appear here
The Body Mass Index is calculated as: BMI = weight (kg) / height (m)^2. In imperial units: BMI = (weight (lbs) * 703) / height (inches)^2. It provides a simple numeric measure of a person's body weight relative to their height.
The WHO classifies BMI into categories: Underweight (below 18.5), Normal weight (18.5 to 24.9), Overweight (25.0 to 29.9), Obesity Class I (30.0 to 34.9), Obesity Class II (35.0 to 39.9), and Obesity Class III (40.0 and above).
BMI is a screening tool, not a diagnostic one. It does not account for muscle mass, bone density, age, sex, or fat distribution. Athletes with high muscle mass may have a high BMI without being overweight. Waist circumference and body fat percentage provide complementary information.
Problem: Calculate the BMI for a person weighing 70 kg and 175 cm tall.
Solution: BMI = 70 / (1.75)^2 = 70 / 3.0625 = 22.86.
Answer: BMI = 22.9 (Normal weight)
Problem: Calculate the BMI for a person weighing 95 kg and 180 cm tall.
Solution: BMI = 95 / (1.80)^2 = 95 / 3.24 = 29.32.
Answer: BMI = 29.3 (Overweight)
Problem: Calculate the BMI for a person weighing 154 lbs and 68 inches tall.
Solution: BMI = (154 * 703) / (68)^2 = 108,262 / 4,624 = 23.42.
Answer: BMI = 23.4 (Normal weight)
Problem: A person at 90 kg and 170 cm loses 5 kg. How does their BMI change?
Solution: Before: BMI = 90 / 1.70^2 = 31.1 (Obese I). After: BMI = 85 / 1.70^2 = 29.4 (Overweight).
Answer: BMI drops from 31.1 to 29.4, moving from Obese I to Overweight
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