BMI (Body Mass Index) is a number calculated from your height and weight that indicates underweight, normal weight, overweight, or obesity.

BMI is a useful guideline for weight relative to height but does not directly measure body fat or muscle. It may misclassify muscular or low-muscle individuals.

BMI Calculator

Q: What are the BMI categories?

BMI categories are: Underweight (<18.5), Normal weight (18.5-24.9), Overweight (25-29.9), Obesity (30+). It is a guideline and does not directly measure fat or muscle.

Q: What is the difference between BMI and body fat percentage?

BMI shows weight relative to height. Body fat percentage estimates how much of your weight is fat, giving a clearer picture of body composition using measurements like waist, neck, height, and hips.

Calculate your Body Mass Index using weight and height.

Body Mass Index (BMI)

What It Means and How to Use It

Body Mass Index (BMI) is a standard screening measurement that relates your weight to your height. It is widely used in healthcare and fitness to provide a general indication of whether a person is underweight, within a normal range, overweight, or obese.
This BMI calculator helps you quickly determine your BMI using either metric or imperial units. After calculation, you will see your BMI value along with its classification category, helping you understand where you fall on the standard BMI scale.
While BMI is not a direct measurement of body fat or muscle mass, it remains a useful first-step indicator for assessing potential weight-related health risks in adults.

Why BMI is used in health assessments

BMI is commonly used because it is simple, fast, and applicable at both individual and population levels. Healthcare professionals use it as an initial screening tool to identify potential risk ranges that may require further evaluation.

When to use this BMI calculator

Use this tool if you want a quick and reliable reference for your weight status, track changes over time, or better understand how your weight compares to standard health ranges.

Check your Body Mass Index (BMI)

BMI Calculation & Results Explanation

Body Mass Index (BMI) formula

BMI is calculated using a standard formula based on weight and height: BMI = weight (kg) / [height (cm) / 100]². You can use either metric or imperial units, and the calculator will provide a quick and reliable result automatically.

BMI Calculation Examples

Metric example: if a person weighs 70 kg and is 175 cm tall, their BMI is 70 / (175 / 100)² ≈ 22.9. This result falls within the Normal Weight category.
Imperial example: if a person weighs 154 lb and is 5 ft 9 in tall, BMI can be calculated as [154 / (5 × 12 + 9)²] × 703 ≈ 22.7. This result also falls within the Normal Weight category.

The Importance of Weight Categories

BMI categories help interpret your result: under 18.5 is considered Underweight,18.5 to 24.9 is Normal Weight, 25 to 29.9 is Overweight, and 30 or higher is classified as Obesity. Being within the normal range is generally associated with a lower risk of conditions such as cardiovascular disease and type 2 diabetes.

Important Limitations of BMI

BMI is useful for screening, but it is not a diagnosis and does not distinguish between fat, muscle, and bone mass. For example, athletes or very muscular individuals may have a high BMI without having excess body fat. For a more complete assessment, BMI should be considered alongside other measurements such as waist circumference and body fat percentage.

Why BMI Is Still Widely Used

BMI remains one of the most widely used screening tools because it is simple, fast, and easy to calculate in both clinical and everyday settings. It can help identify general weight-related patterns at both the individual and population level. Although it does not measure body fat directly, it is still useful as a starting point when interpreted together with other health indicators.

Frequently Asked Questions

What is BMI?

BMI (Body Mass Index) is a number calculated from your height and weight that helps indicate whether you are underweight, normal weight, overweight, or obese. It’s a simple, widely used tool to assess body composition and monitor overall health.

What are the BMI categories?

BMI is classified into different categories:
- Underweight: Less than 18.5
- Normal weight: 18.5 - 24.9
- Overweight: 25 - 29.9
- Obesity: 30 and above.

Note: BMI is a guideline and unitless – it does not directly measure body fat or muscle mass.

Is BMI accurate?

BMI is a useful guideline for assessing body weight relative to height, but it’s not perfect. It does not directly measure body fat or muscle mass, so athletes or very muscular people may appear “overweight” despite being healthy. Use BMI as a quick reference, alongside other measurements like body fat percentage and waist size, to get a more complete picture of your health.

What is the difference between BMI and body fat percentage?

BMI shows how heavy you are for your height, while body fat percentage shows how much of your body is fat.

BMI is a basic calculation based only on height and weight. It compares body weight to height, but it does not measure body fat. Because of this, muscular individuals may be classified as overweight, while people with lower muscle mass and higher fat levels may appear normal.

Body fat percentage focuses directly on body fat and provides a clearer picture of body composition. Methods such as the Navy and RFM formulas estimate body fat using body measurements like waist, neck, height, and sometimes hips.

Is BMI Different for Men and Women?

The BMI formula is the same for men and women because it only considers height and weight.
However, body composition can differ. Women typically have higher body fat percentages than men at the same BMI.
For a more accurate assessment, combine BMI with body fat percentage measurements.