calculate your BMI and weight status based on your age, height and weight.

BMI Calculator

How to Use a Calculator for Calculating BMI

BMI, or body mass index, is a measure of body fat based on your height and weight. It can help you determine whether you are underweight, normal weight, overweight, or obese. Knowing your BMI can also help you assess your health risks and plan your weight management goals.

There are many online tools and apps that can help you calculate your BMI easily. However, if you want to use a calculator for calculating BMI, you need to know the formula and the units of measurement. In this article, we will explain how to use a calculator for calculating BMI in both standard and metric units.

What is the Formula for Calculating BMI?

The formula for calculating BMI is simple: divide your weight by your height squared. However, depending on the units of measurement you use, you may need to apply some conversions or adjustments.

Calculating BMI in Metric Units

If you use metric units, such as kilograms and meters, the formula for calculating BMI is:

BMI = weight in kg / height in m2

For example, if your weight is 73 kg and your height is 1.70 m, your BMI is:

BMI = 73 / 1.702 BMI = 73 / 2.89 BMI = 25.26 kg/m2

Calculating BMI in Standard Units

If you use standard units, such as pounds and inches, the formula for calculating BMI is slightly different:

BMI = weight in lb / height in in2 x 703

The factor of 703 is used to convert the units from lb/in2 to kg/m2. For example, if your weight is 160 lb and your height is 68 in, your BMI is:

BMI = 160 / 682 x 703 BMI = 160 / 4624 x 703 BMI = 24.53 kg/m2

What are the BMI Categories and Ranges?

Once you have calculated your BMI, you can compare it with the standard BMI categories and ranges to see where you stand. The World Health Organization (WHO) recommends the following BMI categories and ranges for adults1:

ClassificationBMI range – kg/m2
Severe Thinness< 16
Moderate Thinness16 – 17
Mild Thinness17 – 18.5
Normal18.5 – 25
Overweight25 – 30
Obese Class I30 – 35
Obese Class II35 – 40
Obese Class III> 40

The BMI categories and ranges may vary slightly depending on factors such as age, gender, ethnicity, and health conditions. For children and teens, the Centers for Disease Control and Prevention (CDC) recommends using BMI-for-age percentiles to assess growth and development2. You can use online tools or charts to find the appropriate BMI percentile for your child or teen.

BMI chart

What are the Benefits and Limitations of Calculating BMI?

Calculating BMI can be a useful way to estimate your body fat and health risks. It can help you monitor your weight status and set realistic goals for weight loss or gain. It can also help you prevent or manage chronic diseases such as diabetes, heart disease, high blood pressure, and some cancers that are associated with being overweight or obese3.

However, calculating BMI also has some limitations. It does not take into account your body composition, such as muscle mass, bone density, or fat distribution. It may overestimate or underestimate your body fat if you are very muscular, very tall or short, pregnant, or have a medical condition that affects your weight or height. It may also not reflect the health risks of different types of fat, such as visceral fat or subcutaneous fat4. Therefore, BMI should not be used as the sole indicator of your health status. You should also consider other factors such as your waist circumference, blood pressure, blood sugar, cholesterol levels, and physical activity levels.


BMI is a simple and widely used measure of body fat based on your height and weight. You can use a calculator for calculating BMI by following the formula and the units of measurement. You can then compare your BMI with the standard categories and ranges to see where you stand. However, you should also be aware of the benefits and limitations of calculating BMI and use other methods to assess your health risks and goals.

BMI Calculator FAQs

BMI stands for body mass index, a measure of whether you’re a healthy weight for your height. It is widely used as a general indicator of whether a person has a healthy body weight for their height. However, BMI may underestimate or overestimate the health risks for some people, such as those who are very muscular, pregnant, or of Asian origin.
To calculate BMI, you need to know your weight in kilograms and your height in meters. Then, you can use this formula: BMI = weight / height^2. For example, if your weight is 75 kilograms and your height is 1.8 meters, then your BMI is 75 / 1.8^2 = 23.15.
The World Health Organization (WHO) has defined the following BMI categories for adults: – Underweight: BMI less than 18.5 – Normal weight: BMI between 18.5 and 24.9 – Overweight: BMI between 25 and 29.9 – Obese: BMI 30 or more
Being overweight or obese increases the risk of a number of serious diseases and health conditions, such as: – Type 2 diabetes – Heart disease – Stroke – High blood pressure – High cholesterol – Certain cancers – Osteoarthritis – Sleep apnea – Gallstones
Having a healthy BMI can help you: – Feel more energetic and confident – Reduce the risk of developing chronic diseases – Improve your mood and mental health – Enhance your physical performance and fitness – Maintain a healthy body image and self-esteem
To improve your BMI, you need to achieve a healthy balance between your calorie intake and expenditure. This means that you need to eat a nutritious and balanced diet that meets your energy and nutritional needs, and engage in regular physical activity that burns calories and builds muscle. Some tips to help you improve your BMI are: – Eat more fruits, vegetables, whole grains, lean proteins, and healthy fats – Avoid or limit processed foods, added sugars, saturated fats, and trans fats – Drink plenty of water and limit alcohol and sugary drinks – Choose smaller portions and eat slowly – Plan your meals and snacks ahead of time – Keep a food diary to track your calories and nutrients – Aim for at least 150 minutes of moderate-intensity or 75 minutes of vigorous-intensity physical activity per week – Include strength training exercises at least twice a week – Find an activity that you enjoy and stick to it – Set realistic and specific goals and monitor your progress
The Ponderal Index (PI) is another measure of body weight that is similar to BMI, but it takes into account the body’s surface area rather than height. It is calculated by dividing the weight in kilograms by the height in meters cubed. The PI can be used to assess the growth of infants and children, as well as the body composition of adults. The PI ranges for adults are: – Underweight: PI less than 12.5 – Normal weight: PI between 12.5 and 15 – Overweight: PI between 15 and 17.5 – Obese: PI 17.5 or more
Our tool is based on the standard formulas and data from the World Health Organization and the Centers for Disease Control and Prevention. However, it is important to note that our tool is not a diagnostic tool and should not be used as a substitute for professional medical advice. There are some factors that can affect the accuracy of our tool, such as: – Measurement errors: Make sure you measure your weight and height accurately and use the same units for both. – Age: Our tool is designed for adults aged 20 or older. For children and teens, please use the BMI calculator for children and teens. – Body type: Our tool assumes you have an average amount of body fat and muscle mass. If you are very muscular or have a larger or smaller frame than average, your BMI may not reflect your true health status. – Ethnicity: Our tool uses the same BMI categories for all ethnic groups, but some ethnic groups may have different health risks at the same BMI level. For example, people of Asian origin may have a higher risk of diabetes and heart disease at a lower BMI than people of Caucasian origin.
To measure your weight and height, you need a reliable scale and a measuring tape or a stadiometer. Here are some tips to ensure accurate measurements: – Weigh yourself in the morning before eating or drinking anything, wearing minimal or no clothing, and using the same scale every time. – Place the scale on a hard and flat surface, not on a carpet or a rug. – Stand on the scale with your feet slightly apart and your weight evenly distributed. Do not lean or hold onto anything. – Record your weight to the nearest 0.1 kilogram or 0.2 pound. – Measure your height without shoes, standing straight with your back against a wall and your head level. – Place a flat object, such as a book or a ruler, on top of your head and mark the point where it meets the wall. – Use a measuring tape or a stadiometer to measure the distance from the floor to the mark. Record your height to the nearest 0.1 centimeter or 0.1 inch.
There is no fixed rule on how often you should check your BMI, but it is recommended that you do it at least once a year as part of your regular health check-up. You can also check your BMI whenever you notice a significant change in your weight or height, or if you have any concerns about your health or weight status. However, you should not obsess over your BMI or use it as the only indicator of your health. Remember that BMI is just one of many factors that affect your health and well-being, and that there are other ways to measure your body composition and fitness level.

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