To calculate BMI, you need to measure weight in kilograms and height in meters. The formula is: BMI = weight (kg) / (height (m)2) For example, if a woman weighs 70 kg and is 1.75 meters tall, her BMI would be: BMI = 70 / (1.75 x 1.75) = 22.86 This value falls within the normal weight range.