Rather than getting stuck on a number on your bathroom scale, pay attention to body mass index (BMI). It’s a ratio of height to weight that indicates if your weight puts your health at risk. To find your BMI, use this formula: Your weight (in pounds), divided by your height in inches squared, multiplied by 703. Or use the on-line BMI calculator below, courtesy of the National Heart, Lung, and Blood Institute: nhlbi.nih.gov.