The simplest method to determine a healthy weight is a measure known as body mass index (BMI). Your BMI classifies you as underweight, normal weight, overweight or obese. You can determine your current BMI by entering your height and weight into an equation, or use an online tool to calculate it. Once you know your BMI you can determine if you need to lose weight and, if so, how much you need to lose to be at a healthy weight.
Step 1
Determine your height in meters. If you only know your height in inches you can convert that number to meters by multiplying it by 2.54 and then dividing that number by 100. For example, a height of 65 inches would be 1.65m.
Step 2
Determine your weight in kilograms. If you only know your weight in pounds divide that number by 2.2 to convert it to kilograms. For example, a weight of 150 lbs. is 68kg.
Step 3
Square your height in meters by multiplying the number by itself. For example, a height of 1.65m would be 2.72 m.
Step 4
Divide your weight in kilograms by your height in meters, squared, to determine your BMI. Using the example a person with a weight of 68kg and height of 1.65m (1.65 x 1.65 = 2.72) would have a BMI of 25. You can also use online BMI calculators such as that provided by the NIH or Centers for Disease Control and Prevention to calculate BMI (see Resources).
Step 5
Use a chart, such as the one provided by the NIH (see Resources), to categorize your BMI. For example, a BMI of below 18.5 is underweight, 18.5 to 24.9 is normal weight, 25 to 29.9 overweight and 30 and above is obese.
Step 6
Determine the appropriate weight for your height to be classified as normal weight. You can do this by plugging lower weights into the BMI equation, but it is easier to look at a BMI Index chart like that provided by the NIH (see Resources). For example, a person with a height of 65 inches should weigh 114 lbs. to 144 lbs. for a normal BMI.
Step 7
Subtract the appropriate weights for a normal BMI range based on your height from your current weight. For example, if you are 65 inches tall and weigh 150 lbs. you would need to lose at least 6 lbs. but no more than 36 lbs. to have a normal weight BMI.
Tips and Warnings
- BMI is only one indicator of health. If you are on the high end of a normal BMI range, eat a healthy diet and exercise regularly there is often no need to lose additional weight. Talk with your health care provider about what your BMI means for your personal health.
- While BMI is a reliable indicator for total body fat related to disease, the National Institutes of Health does admit that there are limitations to this measurement. The BMI calculation can overestimate body fat in muscular athletes and may underestimate the body fat of older individuals or those with reduced muscle mass.
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