From Paul Pruel's blog:How to Determine BMI Without Seeing a Doctor?

If you want to know your weight and determine it if it is healthy weight, overweight, obese and morbidly obese you would need the following: Kilograms or Weigh Scales and a Meter. These are the things needed to determine your Body Mass Index (BMI) or Quetelet index.
read more: http://hitdaxen.blogspot.com/2010/10/how-to-determine-bmi-without-seeing.html