The body mass index, or BMI, can be very helpful in assessing and adjusting your weight. This is not the most accurate measure of the amount of fat in your body, but it is the easiest and cheapest way to measure it. There are different ways to calculate the BMI, according to the measurement system used. You will need to know your height and weight before calculating it.

Click here and find out when BMI may be required.

## Steps

### Method 1 of 4: Using the Metric System

#### Step 1. Measure your height in meters and square it

In other words, just multiply the height value by itself. For example, if you measure 1.75 m, multiply 1.75 by 1.75 and get the approximate sum of 3.06.

#### Step 2. Divide the weight in kilograms by the height value squared

The next step is to divide your fur in kilograms by height in square meters. For example, if you weigh 75 kg and your height squared is 3.06 m, divide 75 by 3.06 and get the number to get your BMI value; in this case 24, 5.

#### Step 3. Use a different equation if your height is in centimeters

It is also possible to calculate BMI with the height value in centimeters, but you will need to use a slightly different formula. The equation is the value of weight in kilograms divided by height in centimeters. Then you need to divide the result again by the height in centimeters and multiply the result by 10,000.

### For example, if you weigh 60 kg and measure 152 cm, divide 60 by 152, then by 152 again (60 / 152 / 152) and get the answer 0. 002596. Multiply this number by 10,000 and get 25, 93, or about of 30. The approximate BMI in this case is 30

### Method 2 of 4: Using the Imperial System

#### Step 1. Measure your height in inches and square it

In other words, just multiply the height value by itself. For example, if you measure 70 inches, multiply 70 by 70. The answer in this example is going to be 4,900.

#### Step 2. Divide your weight in pounds by your height value in square inches

Next, you'll need to divide your fur in pounds by height in square inches. For example, if you weigh 180 pounds, divide 180 by 4,900. The answer is going to be 0.03673.

#### Step 3. Multiply the result by the factorial conversion of 703

To find the BMI value, multiply the last answer by 703. For example, 0.03673 multiplied by 703 equals 25.82; so the approximate BMI, in this example, is 25, 82.

### Method 3 of 4: Using a Metric Conversion Factor

#### Step 1. Multiply the height in inches by 0.025

This number is the conversion factor for transforming inches to meters. For example, if you measure 60 inches, multiply 60 by 0.025 to get 1.5 m.

#### Step 2. Square the last result

Then multiply the last number obtained by itself. For example, if you got the number 1, 5, multiply 1, 5 by 1, 5. In this case, the answer will be 2, 25.

#### Step 3. Multiply the weight in pounds by 0.45

This number is the conversion factor needed to convert pounds to kilograms. It will convert the weight in pounds to its metric equivalent. For example, if you weigh 150 pounds, the kilogram equivalent is 67.5 kg.

#### Step 4. Divide the larger number by the smaller one

Take the number obtained by your weight and divide it by the number obtained by height. In the example used, divide 67, 5 by 1, 5. The answer will be the BMI, in this case 45.

### Method 4 of 4: Knowing When BMI Is Needed

#### Step 1. Calculate your body mass index to see if you are at a healthy weight

BMI is important as it can help identify whether you are underweight, normal, overweight, or obese.

- A BMI less than 18, 5 indicates that you are underweight.
- A BMI between 18, 6 and 24, 9 indicates a healthy weight.
- A BMI between 25 and 29, 9 indicates a weight above the recommended according to height.
- A BMI of 30 or more indicates obesity. If you are obese, see a doctor or lose weight.

#### Step 2. Use BMI to find out if you can have bariatric surgery

In some cases, your body mass index needs to be below a certain value before you can have this surgery. For example, one of the criteria for performing bariatric surgery, among others, is having a BMI between 35 and 40.

#### Step 3. Keep a record of changes in BMI over time

You can use this measurement to track changes in your weight. For example, if you want to record your weight loss, calculating your BMI regularly can be very helpful. Or, if you want to track a child's growth or your own, recording the body mass index is another way to do this.

#### Step 4. Calculate BMI before considering more expensive and invasive options

If you can determine that your body is at a healthy weight using BMI, this may be the best option. However, if you are an athlete or sports lover and believe that BMI is giving an inaccurate picture of your body's fat content, consider taking a different option.

### Some of the options available to determine body fat content are: fat percentage test, hydrodensitometry (or hydrostatic weighing), X-ray biphoton absorptiometry, and bioelectrical impedance. Just keep in mind that these methods are more expensive and invasive than calculating BMI

## Tips

- Maintaining a healthy weight is perhaps the single most important step in achieving better health and a more prosperous life. Calculating your BMI is just an indicator of your general condition and physical health.
- Recent studies have found that waist-to-hip ratio provides a much better indicator of body fat than BMI. Generally, this ratio should not be greater than 0.9 for men and 0.8 for women. A larger number indicates an increased risk of stroke (brain stroke), diabetes and heart attack.
- You can use online calculators like this one.