Why Does Ideal Body Weight Matter?
Ideal body weight is not just about appearance — being over- or underweight both raise the risk of health problems, from heart disease and diabetes to immune system disorders.
The good news is that calculating ideal body weight can be done at home with no special tools. The two most popular methods are the Body Mass Index (BMI) and the Broca formula, which need only your height and weight.
Method 1: Calculating with BMI
BMI (Body Mass Index) is the method recognized by the WHO and Indonesia’s Health Ministry. The formula: BMI = weight (kg) divided by height squared (meters). Example: 70 kg at 170 cm — square the height (1.7 x 1.7 = 2.89), then divide 70 by 2.89 = 24.22 kg/m2.
Interpretation per the Health Ministry: below 17.0 severely underweight; 17.0-18.4 mildly underweight; 18.5-25.0 normal; 25.1-27.0 mildly overweight; and above 27.0 obese. For Asian populations, the normal range is 18.5-22.9.
Method 2: Calculating with the Broca Formula
The Broca formula is simpler because it needs only height and differs by sex. It was introduced by French physician Pierre Paul Broca in 1871. For men: ideal weight (kg) = (height in cm − 100) − 10%. For women: ideal weight (kg) = (height in cm − 100) − 15%.
Example: a man 170 cm tall — (170 − 100) − 10% = 70 − 7 = 63 kg. A woman 158 cm tall — (158 − 100) − 15% = 58 − 8.7 = 49.3 kg. This method is quick but less accurate for very large or very small body sizes.
Limitations of Both Methods
BMI is the fastest method for health providers to assess weight, but it does not distinguish muscle mass from fat. As a result, BMI can misclassify muscular athletes or bodybuilders as overweight.
BMI is also not recommended for evaluating children’s and teens’ weight, pregnant women, people with muscle atrophy, or people over 64. For a comprehensive assessment — including body composition and disease risk factors — consult a doctor or nutritionist.
