Curious about where your weight stands on the health spectrum? Body Mass Index (BMI) is a widely used measure to gauge if your weight is healthy in proportion to your height. Our free BMI Calculator makes it easy to check your score using either metric or imperial units, giving you an instant snapshot of your current standing.

How to Use Our BMI Calculator

Checking your Body Mass Index is a quick and simple process:

1. Select your preferred unit system: Metric (kg, cm) or Imperial (lbs, ft, in).
2. Enter your current weight and height into the corresponding fields.
3. The calculator will instantly show your BMI score and the category your result falls into.

Understanding the BMI Categories

The result of your BMI calculation falls into one of four main categories. This chart shows the standard weight status categories associated with BMI ranges for adults:

Underweight	Below 18.5
Normal weight	18.5 – 24.9
Overweight	25.0 – 29.9
Obesity	30.0 and Above

What Is Body Mass Index (BMI)?

Body Mass Index (BMI) is a simple calculation using a person's height and weight. The formula is `BMI = kg/m²` where `kg` is a person's weight in kilograms and `m²` is their height in metres squared. For a given height, a higher BMI indicates a greater amount of body weight.

Developed by Adolphe Quetelet in the 19th century, BMI is a widely used, inexpensive, and easy-to-perform method of screening for weight categories that may lead to health problems. While it's a useful indicator at the population level, it's important to understand its limitations for individuals.

Limitations of BMI

BMI is a screening tool, not a diagnostic one. It does not directly measure body fat and does not account for the differences between fat and muscle. As a result:

• An athlete or a very muscular person might have a high BMI and be classified as "Overweight" despite having very low body fat.
• An older adult who has lost muscle mass may have a "Normal" BMI but still have an unhealthy level of body fat.

Because of these limitations, BMI should be used as just one piece of a larger health assessment, which should also include factors like diet, physical activity, waist circumference, and family history.

Frequently Asked Questions (FAQ)

Q1: Is this BMI calculator suitable for children?

No. This calculator is designed for adults aged 20 and over. For children and teens, BMI is calculated using the same formula but is then interpreted using age- and sex-specific percentile charts, as body composition changes dramatically during growth and development. Always consult a pediatrician for assessing a child's weight.

Q2: Why doesn't BMI distinguish between fat and muscle?

The BMI formula is based only on height and total weight. It was designed as a simple statistical measure and does not have a way to know the composition of that weight. This is its single biggest limitation. A bodybuilder and a sedentary person of the same height and weight will have the identical BMI, even though their health profiles are completely different.

Q3: What should I do if my BMI is in the "Underweight," "Overweight," or "Obesity" range?

If your BMI falls outside the "Normal" range, it's a good starting point for a conversation with a healthcare professional. They can perform a more comprehensive assessment of your health status and discuss appropriate lifestyle changes, dietary plans, or other measures if necessary. Do not make drastic changes to your diet or exercise routine based solely on a BMI result.