BMI Calculator

Our BMI Calculator helps you understand your body weight in relation to your height, offering a quick insight into whether you're underweight, at a healthy weight, overweight, or obese. It's a simple yet powerful way to set goals for your weight loss programs and track progress toward better health.

Enter your height and weight below to check your BMI

Height

Weight

lbs

Your BMI

0.0

15 18.5 25 30 35 40

What is BMI?

Body Mass Index (BMI) is a widely used metric that defines the relationship between an individual's height and weight to categorize their body composition. It serves as an anthropometric measurement that classifies adults into different groups, such as underweight, normal weight, overweight, or obese. BMI is commonly interpreted as an indicator of an individual's body fat percentage and is used to assess health risks associated with excess or insufficient body weight.

In public health, BMI (Body Mass Index) plays a vital role as it is a key factor in identifying and monitoring population health trends. It helps in determining the risk of several chronic diseases, including hypertension, diabetes, heart disease, cancer, and high cholesterol. Because of its simplicity and wide acceptance, BMI has become a global standard for evaluating weight-related health issues and shaping public health policies.

In addition to adults, childhood BMI is often used to predict potential health outcomes later in life. Researchers also use BMI along with other measurements, such as waist circumference, waist-to-hip ratio, and body fat index, to better understand the relationship between body fat distribution and the risk of developing obesity-related diseases.

If you're unsure where you stand, using a BMI calculator can help you easily find your BMI score. This number allows you to determine whether you're within a healthy weight range or need to take steps for weight loss or weight management. Maintaining a balanced BMI range through a healthy diet, exercise, and lifestyle changes is essential for preventing obesity and improving overall well-being.

How to calculate BMI?

Body Mass Index (BMI) is calculated using a simple mathematical formula that takes into account your weight and height. The calculation method is the same for both adults and children, but the interpretation of results may vary by age and gender in children.

BMI Calculation Formulas by Measurement Units

Measurement Units	Formula & Explanation	Example Calculation
Kilograms and Meters (or Centimeters)	Formula: weight (kg) / [height (m)]² With the metric system, BMI is calculated by dividing weight in kilograms by height in meters squared. If height is measured in centimeters, divide it by 100 to convert it to meters.	Example: Weight = 68 kg Height = 165 cm (1.65 m) Calculation: 68 ÷ (1.65)² = 24.98
Pounds and Inches	Formula: weight (lb) / [height (in)]² × 703 To calculate BMI in imperial units, divide weight in pounds by height in inches squared, then multiply by the conversion factor 703.	Example: Weight = 150 lbs Height = 5'5″ (65″) Calculation: [150 ÷ (65)²] × 703 = 24.96

There are two common systems to calculate BMI, metric and imperial, depending on which measurement units you use.

Using the Metric System (Kilograms and Meters)

Formula: BMI = Weight (kg) / [Height (m)]²

If your height is measured in centimeters, divide it by 100 to convert it to meters.

Example:

Weight = 68 kg

Height = 165 cm = 1.65 m

BMI = 68 / (1.65)² = 24.98

This BMI value (24.98) falls within the healthy weight range.

Using the Imperial System (Pounds and Inches)

Formula: BMI = [Weight (lb) / (Height (in))²] × 703

Here, the number 703 is a conversion factor that adjusts the formula for pounds and inches.

Example:

Weight = 150 lbs

Height = 5'5″ = 65 inches

BMI = (150 / 65²) × 703 = 24.96

Again, this BMI result (24.96) indicates a healthy weight.

If you don't want to do the math manually, you can use an online BMI calculator. Just enter your height and weight, choose your measurement system (metric or imperial), and the calculator instantly shows your BMI score and category (underweight, normal, overweight, or obese).

What do the BMI categories mean?

BMI is a calculation of a person's body weight (in kilograms) divided by the square of their height (in meters). For adults aged 20 and older, BMI categories are used to assess body weight relative to height, regardless of age, sex, or race.

BMI Categories and Ranges

BMI Category	BMI Range (kg/m²)
Underweight	Less than 18.5
Healthy Weight	18.5 to less than 25
Overweight	25 to less than 30
Obesity	30 or greater
Class 1 Obesity	30 to less than 35
Class 2 Obesity	35 to less than 40
Class 3 Obesity (Severe Obesity)	40 or greater

These categories help identify whether an individual is underweight, at a healthy weight, overweight, or obese:

Underweight:

A BMI of less than 18.5 falls into the underweight range. This may indicate that a person is not getting enough nutrients, which can lead to weakened immunity, fatigue, and other health issues.

Healthy Weight:

According to the research, a BMI between 18.5 and less than 25 is considered healthy. This range suggests that a person's weight is appropriate for their height and is associated with a lower risk of chronic diseases.

Overweight:

A BMI between 25 and less than 30 is categorized as overweight. Individuals in this range may have an increased risk of developing conditions like heart disease, high blood pressure, or type 2 diabetes.

Obesity:

When the BMI reaches 30 or above, it is classified as obesity, a BMI of 30 or greater falls under the obesity category. Obesity is divided into three classes, each representing a higher level of risk for serious health problems such as heart disease, stroke, and certain cancers.

Obesity (Grade I–II–III):

Obesity is categorized into three grades based on BMI levels. Grade I (30–34.9) indicates mild obesity, which can often be improved through diet and exercise. Grade II (35–39.9) reflects moderate obesity and may require medical support. Grade III (40 or higher) represents severe obesity, posing serious health risks that might need medical or surgical intervention.

How accurate is BMI in measuring body fat and health risk?

While BMI is a quick and easy way to estimate body fat and potential health risks, it has several limitations that make it less reliable when used alone:

It doesn't distinguish between muscle and fat. A person with high muscle mass, such as an athlete, may fall into the "overweight" or "obese" category despite having low body fat.
It ignores fat distribution. BMI doesn't show where fat is stored. Abdominal (visceral) fat is more dangerous than fat in other areas, but BMI can't detect this difference.
It overlooks metabolic health. BMI doesn't measure factors like blood sugar, cholesterol, or blood pressure, which are critical in determining overall health.
It doesn't account for age, sex, or ethnicity. People of different backgrounds have varying body compositions and health risks at the same BMI level, making one-size-fits-all categories inaccurate.

A Better Way to Measure Health

To overcome these limitations, BMI should be used alongside other indicators such as waist circumference, body composition tests, and metabolic health assessments. These combined tools provide a clearer, more personalized understanding of your true health status.

Want a more accurate picture of your health? Consult with licensed healthcare professionals today.

Formula

703 × weight (lb) ÷ [height (in)]²

Example: 703 × 160 lb ÷ (67 in)² ≈ 25.1

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References

CDC - Body Mass Index NIH - BMI Guidelines

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Reviewed by

Rachel Matthews, MS, RD, CSSD

Rachel is a registered dietitian and board-certified specialist in sports dietetics with over 15 years of experience in clinical and fitness settings. She works with both athletes and individuals pursuing weight management goals, tailoring nutrition plans to support medication-assisted weight loss. Rachel has authored numerous nutrition education materials and brings an evidence-based yet practical perspective to fitness and dietary guidance.