Wraplet guide
How BMI Is Calculated
Understand the BMI formula, how kg and cm are converted, and what BMI categories mean as a general estimate.
BMI formula
BMI means body mass index. It compares weight with height using a simple square-height formula.
BMI = weight in kilograms / (height in meters x height in meters). If height is entered in centimeters, divide it by 100 first.
How to read the result
A BMI below 18.5 is commonly considered underweight, 18.5 to 24.9 normal weight, 25 to 29.9 overweight, and 30 or higher in an obesity range.
BMI is only a screening estimate. It does not measure body fat, muscle mass, pregnancy, age-specific risk, or medical history.
Frequently asked questions
Is BMI medical advice?
No. BMI is a general estimate and should not replace advice from a qualified health professional.
Can BMI be wrong for athletes?
Yes. BMI can read high for people with more muscle because it only uses weight and height.