Figuring Out BMI by Using an Equation

• 1). Determine which formula you will use. The equation that uses standard American measurement units is this:
  
  BMI = (weight in pounds x 703 ) / height in inches²
  
  The metric formula looks like this:
  
  BMI = weight in kilograms / height in meters²
  
  
• 2). Perform the necessary mathematics using your weight. For instance, if you weigh 160 pounds, you would multiply that number times 703, giving you a result of 112,480. The metric equivalent of 160 pounds is 72.7 kilograms. If you're using the metric equation, you don't mutliply kilograms by the number 703; you just leave the kilograms figure (72.7) as is until you get to step 3.
  
  
• 3). Complete the calculations using your height. If you are five-feet-nine-inches tall, this would convert to a total of 69 inches (12 inches in a foot). Now you must square this number:
  
  69 x 69 = 4761.
  
  In the metric formula, 69 inches would equal 1.75 meters. Perform the following equation if you are using the metric formula:
  
  1.75 x 1.75 = 3.06
  
  
• 4). Divide the top figure by the bottom figure. Using the previous example, here's the American equation:
  
  112,480 / 4761 = 23.63
  
  If you're using the metric formula, your figures would look like this:
  
  72.7 / 3.06 = 23.76
  
  Note: The slight variation in the answers will not affect the final categorization.
  
  
• 5). Determine the category in which your answer lies. In this example, an individual with a BMI of 23.76 would be classified as normal weight. If your score places you in the underweight, overweight, or obese categories, you may wish to talk with your doctor about a diet and exercise plan that can help you reach your ideal physical condition.