Buzz
Knowing your Body Mass Index (BMI) allows you to easily evaluate and adjust your weight. Although this number doesn't provide an exact measure of body fat, it is the simplest and most cost-effective method available. There are various ways to calculate your BMI depending on the measurement system you choose. First, you'll need to note your current height and weight to determine your BMI.
Check out the section Why Should You Try This? to understand the benefits of calculating your BMI.
Steps
Measure Using the Metric System
Measure your height in meters and square the result. First, multiply your height in meters by itself. For example, if you are 1.75 meters tall, multiply 1.75 by 1.75 to get a rounded result of 3.06.
Divide your weight in kilograms by your height in meters squared. The next step is to divide your weight in kilograms by your height in meters squared. For example, if your weight is 75kg and your height squared in meters is 3.06, divide 75 by 3.06 to get a BMI of 24.5.
Use a conversion formula if your height is measured in centimeters. You can still calculate your BMI if your height is in centimeters, but you'll need to use a slightly different formula. The formula involves dividing your weight in kilograms by your height in centimeters, then dividing the result by your height in centimeters again, and finally multiplying by 10,000.
- For example, if your weight is 60kg and your height is 152cm, divide 60 by 152, then divide by 152 again (60 / 152 / 152) to get 0.002596. Multiply this by 10,000 to get 25.96, or approximately 26. The BMI in this example is around 26.
- Alternatively, convert your height from centimeters to meters by moving the decimal point two places to the left. For example, 152cm equals 1.52m. Then, calculate your BMI by squaring your height in meters and dividing your weight by the squared height. For example, 1.52 multiplied by 1.52 equals 2.31. If your weight is 80kg, divide 80 by 2.31 to get a BMI of 34.6.
Use the Imperial System
Square your height in inches. To square your height, multiply your height in inches by itself. For example, if your height is 70 inches, multiply 70 by 70 to get 4,900.
Divide your weight by your squared height. Next, divide your weight by your squared height. For example, if your weight is 180 pounds, divide 180 by 4,900 to get 0.03673.
Multiply the result by 703. To calculate your BMI, multiply the result by 703. For example, 0.03673 multiplied by 703 equals 25.82, giving you a BMI of 25.8 in this case.
Convert Measurements to the Metric System
Multiply your height in inches by 0.025. The number 0.025 is the conversion factor to change inches to meters. For instance, if your height is 60 inches, multiply 60 by 0.025 to get 1.5 meters.
Square the result you just obtained. Next, multiply the result by itself. For example, if the result is 1.5, multiply 1.5 by 1.5 to get 2.25.
Multiply your weight in pounds by 0.45. The number 0.45 is the conversion factor to change pounds to kilograms. This step converts your weight to the metric system. For example, if your weight is 150 pounds, the result will be 67.5 kilograms.
Divide the larger number by the smaller one. Take the converted weight and divide it by the squared height. For example, divide 67.5 by 2.25. The result, 30 in this case, is your BMI.
Why Should You Try This?
Calculate your BMI to determine your weight status. BMI is important because it tells you whether you are underweight, overweight, obese, or at a healthy weight.
- A BMI below 18.5 means you are underweight.
- A BMI between 18.6 and 24.9 is considered healthy.
- A BMI between 25 and 29.9 indicates overweight.
- A BMI of 30 or above suggests obesity.
Use BMI to determine if you qualify for weight-loss surgery. In some cases, a specific BMI threshold is required for weight-loss surgery. For example, in the UK, you need a BMI of at least 35 (without diabetes) or 30 (with diabetes) to qualify for such procedures.
Track changes in your BMI. You can use BMI to monitor your weight. For instance, if you're on a weight-loss journey, regularly calculating your BMI can be helpful. Similarly, tracking BMI is useful for monitoring growth in children or personal development.
Calculate your BMI before considering expensive and invasive methods. Individuals with a BMI below 25 are generally considered healthy. However, if your muscle mass is higher than average, your BMI may also be higher. In such cases, a BMI above 25 doesn't necessarily mean you're overweight. If you're muscular, consider measuring skinfold thickness to determine body fat levels.
- In addition to skinfold measurements, underwater weighing, dual-energy X-ray absorptiometry (DXA), and bioelectrical impedance are common methods to assess body fat. Note that these methods are often costly and more invasive than calculating BMI.
Tips
- Another simple way to assess weight status is calculating your waist-to-hip ratio to determine visceral fat, which poses serious health risks.
- If you find it challenging to calculate your BMI manually, use online tools for assistance.
- Maintaining a healthy weight is crucial for overall health and longevity. BMI helps determine if weight loss is necessary. Remember, a BMI above 25 indicates overweight, and a BMI of 30 or higher signifies obesity, which can be harmful to your health.
Warnings
- BMI is relatively useful for individuals aged 25 to 65 but has limitations. It doesn't account for muscle mass or body shape (e.g., apple-shaped or pear-shaped).
What You'll Need
- Health scale
- Tape measure or ruler
- Pencil and paper
- Calculator
