BMI Calculator

Understanding Body Mass Index (BMI)

The Body Mass Index (BMI) is a widely used and critical measurement that assists in understanding one's overall health. It serves as an estimate of body fat and a gauge of the risk for diseases that can occur with more body fat. The higher your BMI, the higher your risk for certain diseases such as heart disease, high blood pressure, type 2 diabetes, gallstones, breathing problems, and certain cancers.

What is BMI?

The Body Mass Index (BMI) is a measurement that uses your height and weight to work out if your weight is healthy. The BMI calculation divides an adult's weight in kilograms by their height in meters squared. For example, if your weight is 70 kilograms and your height is 1.75 meters, your BMI is calculated as 70 ÷ (1.75 x 1.75) = 22.86. The BMI allows health professionals to discuss weight problems more objectively with their patients.

How is BMI Calculated?

For both adult men and women, BMI is calculated the same way. The metric calculation is your weight (in kilograms) divided by your height (in meters) squared. The resulting number is your BMI. To use the table, find the appropriate height in the left-hand column. Move across to a given weight. The number at the top of the column is the BMI for that height and weight.

BMI Calculation Example:

For example, let's say we have an adult female who is 1.65m tall and weighs 65kg. We would first square her height (1.65 x 1.65 = 2.7225). Next, we would divide her weight by this number (65 ÷ 2.7225 = 23.875). So, this individual would have a BMI of approximately 24.

BMI Categories:

Once you have calculated your BMI, you can use this to understand which category you fall into:

  • Underweight: BMI is less than 18.5
  • Normal weight: BMI is 18.5 to 24.9
  • Overweight: BMI is 25 to 29.9
  • Obesity: BMI is 30 or more

Why is Knowing Your BMI Important?

Knowing your BMI can be helpful for a broad range of reasons. It provides a way for you and your doctor to evaluate whether you're underweight, of normal weight, overweight, or obese. Being aware of your BMI can be the first step in taking charge of your overall physical health.

BMI and Health Risks

High BMI is associated with an increased incidence of chronic diseases like heart disease, high blood pressure, stroke, Type 2 diabetes, and certain types of cancer. Research shows that even a modest weight loss, especially in the context of overweight and obesity, can improve these conditions. On the other hand, a lower-than-normal BMI may also increase the risk of health problems like heart failure, respiratory issues, decreased immune function, and osteoporosis. It is crucial to have a balanced BMI, neither too high nor too low.

The Impact of Age and Sex on BMI

While BMI is a useful measurement for most people, it's not accurate for everyone. Age and sex are both factors that can affect BMI. For example, women tend to have more body fat than men for a given BMI. Similarly, older people, on average, tend to have more body fat than younger adults for a given BMI.

Limits of BMI

Despite its usefulness, BMI is not a diagnostic tool. It is a screening measure, and it's possible for individuals to have a high BMI but not have a high amount of body fat. For example, athletes often have a high muscle mass and, therefore, may have a high BMI. Similarly, individuals may have a normal BMI but still have too much body fat, which can also pose health risks. Always consult with your doctor or healthcare provider to understand your BMI in the context of your overall health.


Overall, BMI is a useful indicator of health and a practical way to check if your weight is within a healthy range. Although it is not a definitive measure of body fat nor does it account for factors like age, sex, muscle mass, and distribution of fat, it is a useful starting point. It provides a way for individuals to be mindful of their weight and its implications on their health. It allows people to take preventive measures if they find their weight increasing towards overweight or obese categories. Similarly, it can be a signal to gain weight healthily if an individual falls under the underweight category. Always remember, maintaining a healthy lifestyle is key to having a healthy BMI and overall wellbeing.

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