Quickly calculate your Body Mass Index (BMI) and see where you fall on the BMI chart. This free tool shows whether you’re underweight, at a healthy weight, overweight, or obese—helping you understand health risks and goals.
Calculating BMI takes just three steps
Add height and weight in cm/kg or ft/lbs.
Click calculate for your BMI result.
Compare your score with the BMI index chart for health meaning.
Explore more calculators designed to guide your health:
Metric: BMI = weight (kg) ÷ height² (m) US Units: BMI = (weight lbs ÷ height² in) × 703 Example: A 5’10” (70 in), 160 lb adult → BMI = 23.0 (Normal range).
BMI Prime compares your BMI to the upper “normal” cutoff of 25.
Formula: BMI ÷ 25
Example: BMI 23 ÷ 25 = 0.92 → Normal.
The Ponderal Index (PI) adjusts BMI for very tall or short individuals.
Formula:
Example: 5’10”, 160 lbs → PI = 12.9.
PI is more accurate for extreme body sizes than BMI alone.
In addition to the numeric table, a BMI chart offers a visual representation of the different categories. The chart plots height against weight to show at a glance where underweight, normal, overweight, and obesity thresholds lie. For many people, this makes it easier to see how small changes in weight can shift their BMI classification. Charts are especially useful when comparing across multiple individuals or groups. For example, public health agencies often use BMI charts to study weight trends in the general population. On an individual level, the chart helps people understand how their weight relates to recommended ranges for their specific height, making the results of a BMI calculation more tangible.
The Body Mass Index (BMI) is one of the most widely used tools to assess whether your body weight is appropriate for your height. By dividing weight by height squared, BMI produces a single number that can be compared against health ranges. This number is then used to determine whether someone falls into the underweight, normal, overweight, or obese category. While it does not directly measure body fat, BMI offers a quick and useful way to screen for possible weight-related health risks at both an individual and population level.
Understanding your BMI score can help you take better control of your health journey. While the calculation is straightforward, the meaning behind it can vary depending on age, sex, and ethnicity. For example, men and women with the same BMI may have different body fat percentages, and certain ethnic groups may face higher risks at lower BMI values. Even with these limitations, BMI remains a reliable and accessible indicator that is used worldwide by healthcare providers, researchers, and individuals to track weight status and overall wellness.
For adults age 20 and older, BMI values are categorized into ranges recommended by the World Health Organization (WHO). These categories include severe, moderate, and mild thinness for BMIs under 18.5, a normal weight range between 18.5 and 24.9, overweight between 25 and 29.9, and multiple classes of obesity beginning at 30 and above. This standardized chart applies to both men and women, providing a baseline for determining whether weight is likely to pose health concerns.
The benefit of this table is that it creates a common reference point for health professionals and individuals. Whether you are tracking personal progress, consulting with a doctor, or comparing averages across populations, the adult BMI chart gives a consistent measure of where your body weight falls. While it does not replace more detailed evaluations such as body fat testing, it is often the first step in identifying potential risks tied to weight.
For children and teenagers, BMI is interpreted differently than for adults. Instead of using fixed cutoffs, the Centers for Disease Control and Prevention (CDC) recommend BMI-for-age percentiles that account for growth and development. Children below the 5th percentile are considered underweight, those between the 5th and 85th percentiles are at a healthy weight, those in the 85th to 95th percentile range are at risk of becoming overweight, and those above the 95th percentile are classified as overweight.
These percentiles take into account age and sex, since body composition changes significantly throughout childhood and adolescence. A BMI value that is considered healthy for a teenager may not be the same for a younger child, which is why pediatric growth charts are important. Parents and healthcare providers use these charts to monitor growth patterns and to ensure children remain within healthy ranges as they develop.
Having a BMI of 25 or higher is associated with a range of serious health risks. Being overweight increases the chances of high blood pressure, high LDL cholesterol, and low HDL cholesterol, all of which contribute to cardiovascular disease. It also raises the likelihood of type 2 diabetes, stroke, gallbladder disease, and sleep apnea, conditions that can significantly reduce quality of life. Certain cancers, including breast, colon, kidney, and liver cancer, are also linked to higher BMI levels.
The risks extend beyond physical health. Many people with overweight or obese BMI categories experience joint pain, reduced mobility, and challenges in daily physical activities. Additionally, mental health conditions such as anxiety, depression, and reduced quality of life are more common in individuals with higher BMI scores. These risks underscore the importance of maintaining a BMI below 25, or working with healthcare professionals to develop strategies for achieving a healthier weight.
On the other end of the spectrum, having a BMI below 18.5 can also be harmful. Being underweight may indicate malnutrition, anemia, or vitamin deficiencies, which weaken the body’s ability to function properly. Low BMI is also linked to osteoporosis, a condition where bones become fragile and prone to fractures, and a weakened immune system that makes it harder to fight off infections.
For women, being underweight can disrupt reproductive health by interfering with menstrual cycles and increasing the risk of miscarriage in early pregnancy. Children and teens who are underweight may face delayed growth and development, while adults who undergo surgery may experience more complications during recovery. In some cases, very low BMI may signal an underlying eating disorder or chronic illness, making professional guidance essential.
While BMI is widely used, it does have important limitations. For adults, it measures body weight rather than body fat, which means it cannot distinguish between muscle mass and fat mass. As a result, athletes or muscular individuals may fall into the overweight category despite having low body fat, while older adults may appear to have a healthy BMI despite carrying excess fat. Gender differences also play a role, with women typically having more body fat than men at the same BMI.
For children and teenagers, the limitations are even more pronounced. Factors such as puberty, height, and body composition can all affect BMI readings. Although BMI is still considered a reliable indicator of body fat for most children, it is less accurate for those who fall on the extreme ends of growth percentiles. For this reason, BMI should always be used alongside other health assessments rather than as a sole measure of wellness.
The BMI formula is simple, but it varies depending on whether you use metric or U.S. units. In the metric system, BMI is calculated by dividing weight in kilograms by height in meters squared. In the U.S. system, the formula is weight in pounds divided by height in inches squared, multiplied by 703. Despite the difference in units, both methods produce the same result when converted correctly.
For example, an adult who is 5 feet 10 inches tall (70 inches) and weighs 160 pounds has a BMI of 23, which falls within the normal weight range. By offering both formulas, the BMI calculation can be easily applied regardless of preferred measurement units, making it accessible to a wider audience in both U.S. and international contexts.
BMI Prime is a variation of the standard BMI that compares an individual’s BMI to the upper limit of the normal range, which is 25. The formula simply divides your BMI by 25, giving a value that is easier to interpret across different populations. A BMI Prime below 0.74 indicates underweight, between 0.74 and 1.0 is normal, between 1.0 and 1.2 is overweight, and above 1.2 indicates obesity.
The advantage of BMI Prime is that it shows how far someone is from the normal cutoff. For example, a BMI of 23 divided by 25 equals 0.92, which falls safely in the normal range. This ratio makes it easier to compare health risks among groups with different BMI thresholds, and provides an alternative way of assessing whether weight falls into a risky category.
The Ponderal Index (PI) is another measurement that, like BMI, uses height and weight to evaluate body composition. The key difference is that instead of squaring the height, PI uses height cubed. This adjustment makes PI particularly useful for very tall or very short individuals, where BMI can sometimes give misleading results. For example, BMI often classifies tall individuals as overweight even if they are lean, while PI provides a more balanced evaluation.
In practice, PI is calculated by dividing a person’s weight in kilograms by their height in meters cubed, or by dividing height in inches by the cube root of weight in pounds. Using the same example of a 5’10”, 160-pound adult, the PI result is 12.9. While not as widely used as BMI, PI offers an additional perspective and can help refine weight assessment for people whose body proportions fall outside average ranges.
Most adults fall into the healthy range at 18.5–24.9. This level carries the lowest risk of health complications.
The average American BMI is about 29, which falls in the overweight range. Many adults exceed the healthy threshold.
The formula is the same, but men often carry more muscle, while women typically have higher body fat at the same BMI score.
BMI is a screening tool only. It does not measure fat vs muscle. Body fat percentage gives a clearer health picture.
For ages 2–19, BMI is measured against growth percentiles, not adult categories. Pediatric charts are required for accuracy.
Not always. For example, Asian populations may face higher health risks at lower BMI values. Modified cutoffs may apply.
Talk to a healthcare provider. They can recommend nutrition or activity changes based on your individual health profile.