BMI is a standard height to weight ratio useful for classifying risks associated with weight gain.
BMI= (weight in pounds*703) divided by height in inches squared. Or you can easily google a BMI calculator with your computer and plug in your numbers.
The World Health Organization (WHO) classification has been developed using the following grading system that links increase in BMI to increased health risks.
18.5-24.9 Healthy weight
>40 Severely obese