Enter your height and weight to instantly calculate your Body Mass Index (BMI). See your weight category, understand health risks, and learn what your number really means.
Get your body mass index result in under 30 seconds — in metric or US units.
Type your height and weight into the fields. Use the unit dropdown to choose centimeters, meters, feet, or inches for height — and kilograms or pounds for weight.
Hit the blue Calculate BMI button. The tool automatically converts your inputs to the metric system and applies the standard WHO formula to compute your body mass index score.
Your BMI value and weight category — Underweight, Normal Weight, Overweight, or Obese — appear instantly. Read the sections below to understand what your result means for your health.
Your BMI number places you in one of four weight status categories. Here's what each category means for your health risk and what range to target.
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 values experience reduced mobility, joint pain, and lower energy levels. Mental health can also be affected, with higher rates of depression and anxiety observed in those who are significantly overweight. These risks increase progressively with BMI — a person at BMI 35 faces substantially higher health risk than someone at BMI 26, even though both fall outside the normal range.
BMI is a widely used screening tool, but it has real limitations. The most significant is that 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.
How to calculate your body mass index manually — step by step, using real numbers.
Metric System
BMI = kg ÷ m²
Divide your weight in kilograms by the square of your height in meters.
US / Imperial System
BMI = (lbs ÷ in²) × 703
Divide weight in pounds by height in inches squared, then multiply by 703.
Both formulas produce the same result. The 703 conversion factor accounts for the difference between the metric and imperial measurement systems.
Result Interpretation:
A BMI of 25.8 falls in the overweight range (25.0–29.9). To reach the upper boundary of the healthy range (24.9), this person would need to reduce their weight to approximately 168 lbs — a loss of about 7 pounds. To reach the midpoint of healthy (21.7), the target weight would be approximately 146 lbs.
BMI Prime for this example:
BMI Prime = 25.8 ÷ 25 = 1.03 — just above the overweight threshold of 1.0, confirming the overweight classification.
Practical scenarios where BMI is most helpful — and where you need more context.
If you are an athlete or have a muscular build, your BMI may overestimate body fat. A 5'11" competitive bodybuilder weighing 210 lbs would calculate a BMI of 29.3 — in the overweight range — despite having very low body fat. In this case, body fat percentage (measured via DEXA scan, hydrostatic weighing, or skinfold calipers) is a more meaningful metric than BMI. Your healthcare provider can help determine which measures are most relevant to your situation.
For people over 65, standard BMI cutoffs may underestimate body fat. As adults age, muscle mass naturally decreases and body fat increases — a process called sarcopenic obesity. An older adult with a BMI of 24 may still carry excess visceral fat due to muscle loss. The CDC recommends that older adults also measure waist circumference: risk increases above 35 inches for women and 40 inches for men, regardless of BMI score.
Standard BMI thresholds were developed from primarily European population data. Research consistently shows that Asian Americans face higher risk of type 2 diabetes and cardiovascular disease at lower BMI values. The World Health Organization and many major health organizations recommend lower action thresholds for people of Asian descent: overweight at BMI 23 (instead of 25) and obese at BMI 27.5 (instead of 30). If you are of Asian heritage, discuss appropriate BMI targets with your healthcare provider.
The BMI formula is the same for children, but interpretation requires age- and sex-specific CDC growth charts. A 10-year-old boy at the 50th percentile for BMI has a very different healthy weight range than a 16-year-old girl at the same percentile. Never use adult BMI categories for children — always compare results against the appropriate pediatric chart. The CDC's online BMI calculator for children and teens includes this percentile calculation.
You can use this BMI calculator to work backward and find your healthy weight range. For a person who is 5'6" (66 inches), the healthy BMI range (18.5–24.9) corresponds to a weight range of 115–154 lbs. If you weigh 185 lbs at that height, your BMI is 29.9 — at the top of overweight. Reaching the healthy range requires losing approximately 31 lbs. Research shows that losing just 5–10% of body weight (9–18 lbs in this example) provides meaningful reductions in blood pressure, blood sugar, and cardiovascular risk.
BMI does not reveal where body fat is stored. Visceral fat — the fat stored around your organs in your abdominal region — carries much higher metabolic risk than subcutaneous fat stored under the skin. The CDC and NIH recommend measuring waist circumference alongside BMI. A waist measurement above 35 inches (89 cm) for women or above 40 inches (102 cm) for men indicates elevated metabolic risk even if BMI is in the normal range. Together, BMI and waist circumference give a more complete picture of weight-related health risk.
A BMI number is only useful if it leads to action. Here are concrete next steps based on your result.
Disclaimer: This BMI calculator is a screening tool for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making changes to your diet, exercise routine, or health plan.
Go deeper into your health metrics with these free tools.
Calculate your exact age in years, months, and days from your date of birth.
Convert height between centimeters, meters, feet, and inches instantly.
Find your Total Daily Energy Expenditure to set the right calorie target for weight goals.
Calculate your Basal Metabolic Rate — the calories your body burns at complete rest.
Estimate your body fat percentage using the Navy method — a more detailed metric than BMI alone.
Find your daily calorie needs based on age, height, weight, and activity level.
Common questions about BMI, its limitations, and how to use your result.
For adults 20 and older, the World Health Organization defines a healthy BMI as 18.5 to 24.9. A BMI below 18.5 is underweight, 25.0 to 29.9 is overweight, and 30.0 or above is obese. The healthy range carries the lowest statistical risk of weight-related disease, including type 2 diabetes, heart disease, and certain cancers.
In US units: BMI = (weight in lbs ÷ height in inches²) × 703. For example, someone who is 5'9" (69 inches) and weighs 175 lbs: BMI = (175 ÷ 69²) × 703 = (175 ÷ 4,761) × 703 = 0.03676 × 703 = 25.8 — in the overweight range. Our calculator handles this math for you automatically.
A BMI of 30.0 or higher is classified as obese. The CDC and WHO divide obesity into three classes: Class I (BMI 30.0–34.9), Class II (BMI 35.0–39.9), and Class III or severe obesity (BMI 40.0 and above). Each class carries progressively higher risk of heart disease, type 2 diabetes, hypertension, and other conditions.
The BMI formula is identical for men and women, and the same 18.5–24.9 healthy range applies to both. However, at the same BMI, women naturally carry more body fat than men due to physiological differences. A woman with a BMI of 24 may have 25–31% body fat, while a man with the same BMI may have only 14–20%. This means BMI is a better screening tool for men than women when estimating body fat percentage.
According to the CDC's National Health and Nutrition Examination Survey, the average BMI for American adults is approximately 29.6 — in the overweight range. More than 40% of US adults are classified as obese (BMI 30+), and approximately 73% are overweight or obese. This represents a significant increase from the 1970s, when the average adult BMI was around 25.
BMI is calculated the same way for children ages 2–19, but it is interpreted using age- and sex-specific CDC growth percentiles — not the adult categories. Below the 5th percentile is underweight, 5th–84th is healthy weight, 85th–94th is overweight, and at or above the 95th percentile is obese. Never apply adult BMI categories to children, as the healthy ranges shift significantly with age and development.
A BMI of 25 or above is associated with elevated risk of type 2 diabetes, high blood pressure, high LDL cholesterol, heart disease, stroke, sleep apnea, gallbladder disease, osteoarthritis, and certain cancers including breast, colon, and kidney. Risk increases meaningfully above BMI 30. However, metabolic risk is also influenced by where fat is stored — abdominal (visceral) fat is more dangerous than fat stored in the hips or thighs.
BMI is a useful population-level screening tool, but it has real limitations at the individual level. It cannot distinguish between muscle and fat, so muscular athletes may appear overweight. It does not measure fat distribution — visceral abdominal fat is far more dangerous than fat stored elsewhere. For most adults, BMI correlates reasonably well with body fat percentage, making it a valid first step. For a more complete picture, combine BMI with waist circumference measurement.
Standard BMI thresholds do not apply equally to all ethnic groups. People of Asian descent face higher metabolic risk at lower BMI values — WHO and many health organizations recommend lower thresholds of 23 for overweight and 27.5 for obesity for Asian populations. Research also suggests differences in risk profiles for Hispanic and Black populations. If you are of Asian heritage, discuss ethnicity-adjusted BMI targets with your healthcare provider.
Start with your healthcare provider, who can evaluate your full health picture — including blood pressure, blood glucose, cholesterol, and waist circumference. If you are overweight, research shows that losing just 5–10% of body weight meaningfully reduces cardiovascular and metabolic risk. If you are underweight, a registered dietitian can build a safe plan for healthy weight gain. Avoid extreme diets in either direction — gradual, sustainable changes produce better long-term outcomes.