Knowing your "Body Mass Index", or BMI, can be helpful in understanding how to change your body weight. While not the most accurate indicator for evaluating the amount of fat in the body, it is still a simple and inexpensive tool that can provide you with this information. There are a number of different methods for calculating BMI, which vary according to the measurement system adopted. Before you begin, make sure you have your current height and weight data handy.
Check out this section of the article to find out how to correctly interpret your BMI.
Steps
Part 1 of 3: Using the Metric System
Step 1. Measure your height in meters, then square it
To do this, multiply your height in meters by itself. For example, if you are 1.75m tall, you will need to do the following multiplication: 1.75 x 1.75, yielding an approximate result of 3.06.
Step 2. Divide your weight in kilograms by the square of your height
The next step is to find your weight in kilograms and divide it by the square of your height in meters. For example, if your weight is 75 kg, and the square of your height is 3.06, then doing the calculations will give you 75/3.06 = 24.5. So your BMI equals 24.5
The equation is kg / m2, where kg is your weight in kilograms and m is your height in meters.
Step 3. Use a different equation if your height is in centimeters
Even if your height is expressed in centimeters, you can still calculate your BMI, but you need to slightly modify the equation used. In this case, the formula requires you to divide your weight in kilograms by your height in centimeters. The result obtained will then have to be divided again by your height in centimeters and multiplied by 10,000.
- For example, if your weight is 60 kg and you are 152 cm tall, you will have to proceed with the following calculation: (60/152) / 152, obtaining as a result 0, 002596. At this point you will have to multiply this last figure by the coefficient 10,000, resulting in 25, 96, which can be rounded up to 26.
- Another option is to simply convert the height from centimeters to meters, which you can do by moving the decimal two digits to the left. For example, 152 centimeters equals 1.52 meters. Then, calculate your BMI by squaring your height in meters and finally dividing your weight by the square of your height. For example, 1.52 multiplied by itself results in 2.11. If you weigh 80 kg, then you would divide 80 by 2.11 to get a BMI of 34.6.
Part 2 of 3: Using the Anglo-Saxon Units of Measure
Step 1. Calculate the square of your height in inches
To do this, multiply your height value by itself. For example, if you are 70 inches tall, do the following: 70 x 70, resulting in 4900.
Step 2. Divide your weight by your height
The next step is to divide your weight (in pounds) by the square of your height. For example, if you weigh 180 pounds, the calculation to be made will be the following: 180/4900, resulting in 0, 03673.
The equation is weight / height2
Step 3. Multiply the value obtained in the previous step by the coefficient 703
To calculate your BMI, you need to multiply the previous result by 703. Following our example, you need to multiply 0.03673 x 703 to get 25.82. Rounded off, the example BMI is 25.8.
Part 3 of 3: Interpreting the Results
Step 1. Calculate your BMI to determine if your body weight is healthy
BMI is an important biometric parameter as it can help you determine if you are underweight, normal, overweight or obese.
- A BMI below 18.5 indicates an underweight state.
- A BMI between 18.5 and 24.9 indicates an ideal body weight.
- A BMI between 25 and 29.9 indicates a state of overweight.
- A BMI greater than 30 indicates obesity.
Step 2. Use your BMI to determine if you are a possible candidate for bariatric surgery
In some situations, the BMI must be above a certain value to have access to the solutions provided by bariatric surgery. For example, in Italy, to have access to this type of treatment, it is necessary to have a BMI greater than 40 or between 35 and 39.9, if associated with diseases related to obesity. In the UK, on the other hand, you must have a BMI above 35, unless you have diabetes, or at least 30 if you have diabetes.
Step 3. Monitor your BMI changes
BMI can help you examine how your body weight varies over time. For example, if you want to graph how your weight decreases during a diet, calculate your BMI at regular intervals. Likewise, if you need to supervise a child's growth, or your own, BMI can be a very useful tool.
Step 4. Calculate your BMI before considering more expensive and invasive options
If you can determine that your body weight is within a range of values that are considered healthy, you can consider proceeding no further. However, if you are an athlete or a person who spends a lot of time in sports, and you feel that BMI is not a good indicator for determining body fat mass, you can consider other approaches.
Plicometry, hydrostatic weighing, DXA (Dual-energy X-ray Absorptiometry) and bio-impedancemetry are some of the options available to measure body fat mass. However, remember that these are very expensive and invasive techniques compared to simply calculating BMI
Advice
- Maintaining a healthy body weight is probably the most important step you can take to live long health. BMI is simply biometric data that roughly indicates an individual's general physical and health condition.
- Another very simple method of determining if you have a healthy body weight is to calculate your waist-to-hip ratio.
