How to Calculate Weight and BMI
- 1). Weigh yourself first thing in the morning after using the bathroom. Your weight can fluctuate by as much as 5 lbs. during the day because of bloating, food intake and fluid retention. Weighing yourself first thing in the morning before you eat ensures you'll get the most accurate result. Also, be sure your scale sits on a hard, flat surface. Carpeting can throw your reading off by as much as 20 pounds.
- 2). Use the equation. Multiply your weight in pounds by 703. Divide that result by your height in inches. Divide that result again by your height in inches to calculate your BMI. For example, a 150-pound woman who is 5'5" would calculate this way: 150 x 703 = 105,450. 105,450/65 inches = 1622.31. 1622.31/65 inches = 24.95. Her BMI is 24.9.
- 3). Check yourself against an online calculator. Once you have calculated your BMI manually, it's a good idea to check your answer for accuracy by using an online calculator. It will ask you to enter your height and weight, and it will calculate your BMI instantly. Check this result against the answer your answer; they should be the same.
- 4). Determine what category you fall in. Those with BMIs below 18.5 are considered underweight. A BMI of 18.5 to 24.9 is normal. If your BMI is between 25.0 and 29.9, you are classified as overweight. Anything above 30.0 is considered obese.
- 5). Evaluate your results. According to the National Center for Health Statistics, more than 64 percent of adults in the United States have a BMI of greater than 25, classifying them as overweight or obese. Obesity increases risk factors for various conditions and diseases such as diabetes, high blood pressure, heart disease, sleep apnea and high cholesterol. If you fall into one of these categories, it is important to take steps to reduce your body fat and help prevent disease.
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