Measure height (in meters or centimeters)
Measure weight (in kilograms)
Use the BMI formula: BMI = weight (kg) / (height (m) × height (m))
If height is in centimeters, convert to meters: height (m) = height (cm) / 100
Calculate BMI
Compare the result with common categories:
Underweight: BMI < 18.5
Normal: BMI 18.5–24.9
Overweight: BMI 25.0–29.9
Obesity: BMI 30.0 or higher
Severe obesity: BMI 40.0 or higher
Use an online BMI calculator if preferred
Recheck using the same units each time
Record height and weight values used for the calculation