Calculate your Body Mass Index (BMI) to see if you're at a healthy weight. BMI is a simple measure using your height and weight. Use this free BMI calculator for women, men, adults of any age, or children to get instant results with detailed health guidance.
—
The World Health Organization (WHO) defines the following BMI categories for adults. These categories help healthcare professionals and individuals assess weight status relative to height. For a deeper dive into how these ranges apply to you, read our complete BMI calculator guide.
| Category | BMI Range (kg/m²) | Risk Level |
|---|---|---|
| Severe Thinness | < 16.0 | High |
| Moderate Thinness | 16.0 – 16.9 | Moderate |
| Mild Thinness | 17.0 – 18.4 | Low |
| Normal Weight | 18.5 – 24.9 | Minimal |
| Overweight | 25.0 – 29.9 | Increased |
| Obese Class I | 30.0 – 34.9 | High |
| Obese Class II | 35.0 – 39.9 | Very High |
| Obese Class III | ≥ 40.0 | Extremely High |
Source: World Health Organization — Obesity and Overweight Fact Sheet. BMI categories for women and men use the same ranges, though health risks at each level may differ by sex.
The table below shows approximate BMI values for common height and weight combinations using the imperial formula. Find your height on the left and your weight across the top. Cells are color-coded: green = normal, yellow = overweight, orange = obese class I, red = obese class II+. For the full BMI formula explanation, see our detailed guide. Also see our charts for women and men.
| Height | 100 lbs 45 kg |
110 lbs 50 kg |
120 lbs 54 kg |
130 lbs 59 kg |
140 lbs 64 kg |
150 lbs 68 kg |
160 lbs 73 kg |
170 lbs 77 kg |
180 lbs 82 kg |
190 lbs 86 kg |
200 lbs 91 kg |
210 lbs 95 kg |
220 lbs 100 kg |
230 lbs 104 kg |
240 lbs 109 kg |
250 lbs 113 kg |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 4'10" | 20.9 | 23.0 | 25.1 | 27.2 | 29.3 | 31.4 | 33.5 | 35.6 | 37.7 | 39.8 | 41.8 | 43.9 | 46.0 | 48.1 | 50.2 | 52.3 |
| 5'0" | 19.5 | 21.5 | 23.4 | 25.4 | 27.3 | 29.3 | 31.2 | 33.2 | 35.2 | 37.1 | 39.1 | 41.0 | 43.0 | 44.9 | 46.9 | 48.8 |
| 5'2" | 18.3 | 20.1 | 22.0 | 23.8 | 25.6 | 27.4 | 29.3 | 31.1 | 32.9 | 34.8 | 36.6 | 38.4 | 40.3 | 42.1 | 43.9 | 45.7 |
| 5'4" | 17.2 | 18.9 | 20.6 | 22.3 | 24.0 | 25.8 | 27.5 | 29.2 | 30.9 | 32.6 | 34.3 | 36.1 | 37.8 | 39.5 | 41.2 | 42.9 |
| 5'6" | 16.1 | 17.8 | 19.4 | 21.0 | 22.6 | 24.2 | 25.8 | 27.4 | 29.1 | 30.7 | 32.3 | 33.9 | 35.5 | 37.1 | 38.7 | 40.4 |
| 5'8" | 15.2 | 16.7 | 18.2 | 19.8 | 21.3 | 22.8 | 24.3 | 25.8 | 27.4 | 28.9 | 30.4 | 31.9 | 33.4 | 35.0 | 36.5 | 38.0 |
| 5'10" | 14.3 | 15.8 | 17.2 | 18.7 | 20.1 | 21.5 | 23.0 | 24.4 | 25.8 | 27.3 | 28.7 | 30.1 | 31.6 | 33.0 | 34.4 | 35.9 |
| 6'0" | 13.6 | 14.9 | 16.3 | 17.6 | 19.0 | 20.3 | 21.7 | 23.1 | 24.4 | 25.8 | 27.1 | 28.5 | 29.8 | 31.2 | 32.6 | 33.9 |
| 6'2" | 12.8 | 14.1 | 15.4 | 16.7 | 18.0 | 19.3 | 20.5 | 21.8 | 23.1 | 24.4 | 25.7 | 27.0 | 28.3 | 29.5 | 30.8 | 32.1 |
| 6'4" | 12.2 | 13.4 | 14.6 | 15.8 | 17.1 | 18.3 | 19.5 | 20.7 | 21.9 | 23.2 | 24.4 | 25.6 | 26.8 | 28.1 | 29.3 | 30.5 |
Weight shown in pounds (lbs) across the top row. BMI = (weight × 703) / height². Values rounded to one decimal place.
Body Mass Index is a mathematical ratio of weight to height. It was devised in the 1830s by Belgian mathematician Adolphe Quetelet and remains the most widely used population-level screening tool for weight status. Understanding the BMI formula helps you interpret your results more accurately.
BMI = weight (kg) ÷ height (m)²
Worked example: A person who weighs 70 kg and is 1.75 m tall:
BMI = 70 ÷ (1.75 × 1.75) = 70 ÷ 3.0625 = 22.9 (Normal weight)
BMI = (weight (lbs) × 703) ÷ height (in)²
Worked example: A person who weighs 160 lbs and is 5'7" (67 inches) tall:
BMI = (160 × 703) ÷ (67 × 67) = 112,480 ÷ 4,489 = 25.1 (Overweight)
The number 703 bridges the gap between imperial and metric units. One kilogram equals approximately 2.20462 pounds, and one meter equals approximately 39.3701 inches. When you work through the unit conversion mathematically — dividing 39.3701² by 2.20462 — you get approximately 703.06, which is rounded to 703 for practical use. This factor ensures that using pounds and inches produces the same BMI as using kilograms and meters. For a complete walkthrough of all variations, see our BMI formula explained guide.
In 2013, mathematician Nick Trefethen of Oxford University proposed an updated formula: BMI = 1.3 × weight (kg) ÷ height (m)2.5. This revised formula was designed to address the traditional formula's tendency to make shorter people think they are thinner than they are and taller people think they are fatter. While interesting, this new formula has not been adopted by the WHO or major health organizations, so the standard formula remains the clinical standard.
While BMI is a useful and widely accessible screening tool, it has well-documented limitations that you should understand when interpreting your results. BMI is best used as a starting point, not a definitive health assessment.
BMI cannot distinguish between muscle mass and fat mass. Athletes and bodybuilders often register as "overweight" or "obese" despite having low body fat. A lean body mass calculator gives a better picture in these cases.
BMI does not account for age-related changes in body composition. Older adults tend to have more fat and less muscle. Women naturally carry more body fat than men. Use our BMI by age calculator for adjusted ranges.
Health risks at the same BMI level vary across ethnic groups. Asian populations experience elevated risks at lower BMI values, which is why some countries use a BMI cutoff of 23 for overweight rather than 25.
BMI is not suitable as a health measure during pregnancy. Weight gain during pregnancy is normal and necessary. Pre-pregnancy BMI is used to determine recommended weight gain ranges instead.
BMI may underestimate health risks in older adults who have lost muscle mass (sarcopenia). An older person with a "normal" BMI may actually have a high body fat percentage and significant metabolic risk.
BMI may overestimate body fat in athletes and individuals with high muscle mass. A football player with a BMI of 30 is not the same as a sedentary person with a BMI of 30. Body fat percentage or DEXA scans are more appropriate for athletes.
For a comprehensive health assessment, pair BMI with waist circumference, body fat percentage, blood pressure, cholesterol, and blood sugar measurements. Learn more about BMI's limitations from these authoritative sources:
Your BMI category can provide a general indication of health risks. Below is a detailed overview of the potential health consequences associated with each weight status category. For personalized guidance, see our calculators for women, men, or by age. Read our healthy BMI range guide for more detail.
Being underweight carries significant health risks that are often underappreciated. Individuals with a BMI below 18.5 may experience malnutrition and vitamin deficiencies, a weakened immune system leading to increased susceptibility to infections, osteoporosis and increased fracture risk, anemia, fertility problems in both women and men, and delayed wound healing. Severe underweight (BMI < 16) is associated with significantly increased mortality risk. Underlying causes can include eating disorders, thyroid disorders, celiac disease, or other chronic illnesses. If your BMI is below 18.5, consult a healthcare provider to investigate potential causes and develop a healthy weight gain plan.
Carrying excess weight in the overweight range increases the risk of developing several chronic conditions. These include type 2 diabetes (risk increases even within the upper-normal BMI range), cardiovascular disease including hypertension and elevated cholesterol, sleep apnea, joint problems especially in the knees and hips, gallbladder disease, and certain cancers including colon, breast (post-menopausal), and kidney cancers. However, the overweight category is also where BMI's limitations are most apparent — some people in this range are metabolically healthy, particularly those who exercise regularly and have favorable waist circumference measurements. Find your ideal weight using clinical formulas for a more personalized target.
Obesity significantly raises the risk and severity of numerous health conditions. The risks increase progressively through Class I (BMI 30-34.9), Class II (BMI 35-39.9), and Class III (BMI ≥ 40) obesity. Associated health risks include a markedly increased risk of type 2 diabetes (up to 7x for Class III), coronary heart disease and stroke, metabolic syndrome, respiratory problems including severe sleep apnea, non-alcoholic fatty liver disease (NAFLD), chronic kidney disease, mental health challenges including depression and reduced quality of life, increased surgical and anesthetic risk, and reduced life expectancy. Research from the Mayo Clinic shows that even modest weight loss of 5-10% of body weight can significantly improve health markers. The Harvard Health Blog provides additional context on how BMI relates to actual health outcomes.
For a more comprehensive perspective on how BMI connects to disease risk, see the Cleveland Clinic's BMI overview and our in-depth BMI calculator guide.
BMI is just one of several tools used to assess body composition and health risk. Each metric has strengths and weaknesses. Understanding how they compare helps you choose the right tool — or combination of tools — for your situation. For body composition analysis, try our lean body mass calculator.
| Metric | What It Measures | Pros | Cons | Best For |
|---|---|---|---|---|
| BMI | Weight-to-height ratio | Free, easy to calculate, well-researched | Doesn't distinguish fat from muscle | Population screening, general health check |
| Waist Circumference | Abdominal fat distribution | Strong predictor of metabolic risk, easy to measure | Doesn't account for height, measurement varies | Assessing abdominal obesity, cardiovascular risk |
| Waist-to-Hip Ratio | Fat distribution pattern (apple vs. pear shape) | Better predictor of heart disease than BMI alone | Doesn't measure total fat, requires two measurements | Heart disease risk, fat distribution analysis |
| Body Fat % | Percentage of total weight that is fat | Directly measures what BMI estimates, distinguishes fat from lean mass | Accuracy depends on method (calipers, bioimpedance, etc.) | Athletes, fitness tracking, medical assessment |
| DEXA Scan | Fat, muscle, and bone mass by body region | Gold standard accuracy, regional breakdown, tracks changes | Expensive ($75-200+), requires clinical visit, minor radiation | Clinical research, osteoporosis screening, serious athletes |
The best approach is to use multiple metrics together. For example, combine your BMI result with a waist circumference measurement and, if available, a body fat percentage estimate from our lean body mass calculator. This gives a much more complete picture than any single number.
While the WHO's standard BMI categories are used globally, research has shown that health risks associated with a given BMI vary by ethnicity and geography. This has led some countries and health organizations to adopt modified cutoffs.
Asian populations tend to accumulate visceral (abdominal) fat at lower BMI levels than Caucasian populations. As a result, the WHO's Western Pacific Region and many Asian countries use adjusted thresholds: a BMI of 23 is considered overweight and 27.5 is considered obese, compared to 25 and 30 in the standard classification. Countries including Japan, China, India, and Singapore have adopted these lower cutoffs in their national health guidelines.
Pacific Islander and Polynesian populations tend to have greater bone density and muscle mass, which means standard BMI cutoffs may overestimate their body fat. Some health agencies in New Zealand and Pacific island nations use higher thresholds, with overweight beginning at 26 and obesity at 32.
African and African-American populations may also have different body compositions that affect BMI interpretation. Some studies suggest that at the same BMI, Black individuals may have less visceral fat and more muscle mass compared to White individuals of the same age and sex.
The key takeaway is that BMI is a useful population-level tool, but its interpretation should consider ethnic background. If you have questions about how BMI applies to your specific situation, speak with your healthcare provider. For more information, see the WHO fact sheet on obesity and overweight and our guide on BMI by age.
While a BMI calculator is a helpful self-screening tool, certain results and circumstances warrant professional medical consultation. Consider scheduling an appointment with your healthcare provider in the following situations:
Your doctor can perform a comprehensive health assessment that goes far beyond what a BMI number alone can tell you. This typically includes blood tests (cholesterol, blood sugar, thyroid function), blood pressure measurement, physical examination, and a discussion of your lifestyle, family history, and health goals. Remember: BMI is a starting point for conversation, not a diagnosis. For children and teens, always consult a pediatrician to interpret BMI percentile results in the context of growth and development.
Our suite of specialized BMI and body composition calculators helps you get a more nuanced picture of your health. Each calculator is designed for a specific purpose:
BMI calculator with women-specific healthy weight ranges and recommendations. Accounts for the fact that women naturally carry a higher body fat percentage than men, and provides tailored guidance for each life stage including menopause considerations.
BMI calculator with men-specific healthy weight ranges and recommendations. Addresses the unique body composition patterns in men, including the tendency to store fat abdominally, and provides waist circumference guidelines specific to male health thresholds.
Age-adjusted BMI calculator with recommendations for different life stages. Recognizes that body composition changes with age — older adults may benefit from a slightly higher BMI, while younger adults can reference standard ranges.
BMI percentile calculator for children and teens ages 2-19. Uses CDC growth charts to compare your child's BMI to age- and sex-matched peers, with clear percentile explanations and growth tracking guidance.
Calculate your ideal body weight using multiple clinical formulas including Devine, Robinson, Miller, and Hamwi. Compares results across formulas to give you a well-rounded target weight range rather than a single number.
Estimate your lean body mass, fat mass, and body fat percentage. Uses the Boer, James, and Hume formulas to calculate how much of your weight is muscle, bone, and organs versus stored fat — ideal for athletes and fitness enthusiasts.
Calculate your BMI using the updated 2013 Trefethen formula that corrects the traditional formula's height bias. Compare your New BMI side-by-side with traditional BMI to see if your category changes.
Medical Disclaimer: This calculator provides estimates for informational purposes only. BMI is a screening tool, not a diagnostic measure. It does not account for muscle mass, bone density, age, sex, or ethnicity. Always consult a healthcare professional for medical advice. The information on this page should not be used as a substitute for professional medical advice, diagnosis, or treatment.
BMI (Body Mass Index) is a numerical value calculated from your weight and height. Devised in the 1830s by Belgian mathematician Adolphe Quetelet, it is used worldwide as a screening tool to categorize weight status into underweight, normal weight, overweight, and obese categories. While it doesn't directly measure body fat, extensive research has shown it correlates with more direct measures of body fat and with health outcomes at the population level. Learn more in our complete BMI guide.
BMI is calculated by dividing your weight in kilograms by your height in meters squared: BMI = weight (kg) / height (m)². In imperial units: BMI = (weight in lbs × 703) / height in inches². The factor of 703 converts the imperial formula to produce the same result as the metric formula. For example, a person who is 5'10" (70 inches) and weighs 180 lbs would have a BMI of (180 × 703) / (70²) = 126,540 / 4,900 = 25.8. Read our BMI formula explained guide for detailed examples.
For most adults, a healthy BMI falls between 18.5 and 24.9. This range is associated with the lowest risk of weight-related health conditions. Below 18.5 is classified as underweight, 25-29.9 is overweight, and 30 or above is obese. However, "healthy" BMI can vary based on factors like age, sex, ethnicity, and muscle mass. Some research suggests that for older adults, a slightly higher BMI (up to 27) may be protective. For Asian populations, a BMI above 23 is considered overweight due to higher metabolic risks at lower weights. Check our healthy BMI range guide for a full breakdown.
Yes. For children and teens aged 2-19, BMI is interpreted using age- and sex-specific percentiles rather than the fixed adult cutoffs. The same BMI number means very different things at different ages because body composition changes dramatically during growth. A child at the 85th to 94th percentile is considered overweight, and at or above the 95th percentile is considered obese. Below the 5th percentile is underweight. Pediatric BMI is plotted on CDC growth charts to track a child's trajectory over time. See our BMI by age guide for more details.
Both are valuable, and they're best used together. BMI gives you an overall weight status, while waist circumference specifically measures abdominal fat, which is more strongly linked to heart disease, type 2 diabetes, and metabolic syndrome. According to the NIH, men should aim for a waist circumference below 40 inches (102 cm) and women below 35 inches (88 cm). Someone with a "normal" BMI but a high waist circumference may be at greater risk than their BMI alone suggests. The combination of BMI and waist circumference provides a more complete risk assessment than either measure alone.
Yes. This condition is sometimes called "normal weight obesity" or being "skinny fat." It occurs when someone has a BMI in the healthy range but a high body fat percentage and low muscle mass. Studies have shown that approximately 30% of people with normal BMI may have metabolic abnormalities typically associated with obesity, including high blood pressure, elevated blood sugar, and unfavorable cholesterol levels. This underscores why BMI should be used alongside other assessments. Try our lean body mass calculator to get a better understanding of your body composition.
For adults with stable weight, checking your BMI a few times per year is sufficient. If you're actively trying to lose or gain weight, monthly checks can help track your progress. It's more useful to focus on trends over time rather than individual measurements, since daily weight fluctuations of 2-4 lbs are normal due to water retention, food intake, and other factors. Weigh yourself at the same time of day (ideally in the morning) for the most consistent results. For children, BMI should be tracked at regular pediatric checkups, typically annually.
Yes, being underweight (BMI < 18.5) carries serious health risks including malnutrition, weakened immune system, osteoporosis, anemia, fertility issues, and increased mortality risk. Research shows that severely underweight individuals (BMI < 16) face mortality risks comparable to those with Class III obesity. Causes of low BMI can include eating disorders, hyperthyroidism, celiac disease, cancer, infections, or simply insufficient caloric intake. If your BMI is below 18.5, it's important to consult a healthcare provider to identify any underlying conditions and develop a safe weight gain plan. See our ideal weight calculator for a healthy target.
No, BMI frequently misclassifies athletes. Because BMI cannot distinguish between muscle and fat, individuals with high muscle mass often show elevated BMI despite having low body fat. For example, many NFL running backs have a BMI over 30 (technically "obese") while having body fat percentages under 12%. Similarly, bodybuilders, rugby players, and other strength athletes are routinely misclassified. For athletes and active individuals, body fat percentage (measured via calipers, bioimpedance, or DEXA scan) and our lean body mass calculator are more appropriate metrics. Waist circumference can also help distinguish muscular from obese individuals with the same BMI.
Yes, health risks at the same BMI level vary significantly across ethnic groups. Asian populations develop obesity-related conditions at lower BMI values, prompting the WHO Western Pacific Region to recommend overweight cutoffs of 23 (vs. 25) and obesity cutoffs of 27.5 (vs. 30). Pacific Islander and Polynesian populations have greater bone density and muscle mass, potentially making standard cutoffs too restrictive. Black individuals tend to have greater bone mineral density and muscle mass at the same BMI. These differences highlight that BMI is a population-average tool, and individual interpretation should consider ethnic background. Consult the WHO guidelines for more information.
In 2013, Oxford mathematician Nick Trefethen proposed an updated BMI formula: BMI = 1.3 × weight (kg) / height (m)2.5. The traditional formula (weight / height²) tends to make shorter people think they are thinner than they are and taller people think they are fatter, because it uses height squared rather than a higher exponent. Trefethen's formula raises the height exponent to 2.5 and adds a multiplication factor of 1.3 to compensate. While this produces arguably fairer results across different heights, it has not been adopted by the WHO, CDC, or any major health organization. The standard formula remains in clinical use worldwide. Read more in our BMI formula explained guide.
At the population level, yes — BMI is a statistically significant predictor of many health outcomes. Large epidemiological studies consistently show that both very low and very high BMI values are associated with increased mortality, cardiovascular disease, type 2 diabetes, certain cancers, and other chronic conditions. The relationship follows a J-shaped or U-shaped curve, with the lowest risk around a BMI of 22-25. However, at the individual level, BMI is less predictive because it doesn't capture important factors like fat distribution, fitness level, metabolic markers, and genetics. A person with a BMI of 27 who exercises regularly, has normal blood pressure and blood sugar, and carries weight in their hips rather than their abdomen may be healthier than a sedentary person with a BMI of 23. This is why medical professionals use BMI as one tool among many. For more context, read the Harvard Health perspective on BMI.
Explore our in-depth articles for more information about BMI, body composition, and healthy weight management:
The complete guide to understanding and using BMI calculators, including step-by-step calculation examples, chart interpretation, and practical tips for healthy weight management.
Women-specific BMI chart with healthy weight ranges by height, age-related adjustments, and guidance on how body composition differs for women across life stages.
Men-specific BMI chart with healthy weight ranges by height, waist circumference guidelines, and information on how muscle mass affects BMI interpretation for men.
Detailed walkthrough of the BMI formula in both metric and imperial units, worked examples, the significance of the 703 conversion factor, and the proposed new BMI formula.
Everything you need to know about what constitutes a healthy BMI range, how it varies by age, sex, and ethnicity, and what the science says about optimal BMI for longevity.
How BMI interpretation changes across age groups, from pediatric percentile-based assessment through adult ranges to age-adjusted recommendations for older adults.
Body Mass Index (BMI) has been the standard screening tool for weight classification since the World Health Organization (WHO) adopted it in the 1990s. Originally developed by Belgian mathematician Adolphe Quetelet in the 1830s, BMI provides a simple way to assess whether an individual's weight falls within a healthy range relative to their height. According to the Centers for Disease Control and Prevention (CDC), BMI is used because it correlates reasonably well with more direct measures of body fat, such as underwater weighing and dual-energy X-ray absorptiometry (DEXA). Understanding your BMI is the first step toward making informed decisions about your health, whether you're using our BMI calculator for women or BMI calculator for men.
The relationship between BMI and health outcomes has been extensively studied. Research published by the National Heart, Lung, and Blood Institute (NHLBI) demonstrates that as BMI increases above the normal range, so does the risk of cardiovascular disease, type 2 diabetes, hypertension, and certain cancers. The Mayo Clinic notes that even modest weight loss of 5-10% of body weight can lead to significant improvements in blood pressure, cholesterol levels, and blood sugar control. For those looking to understand their ideal weight target, our healthy BMI range guide provides detailed information about optimal weight ranges for different populations.
However, it's crucial to understand that BMI is a screening tool, not a diagnostic measure. As Harvard Health explains, BMI cannot distinguish between muscle mass and fat mass, which is why athletes and bodybuilders often appear "overweight" or "obese" by BMI standards despite having low body fat. Additionally, BMI doesn't account for fat distribution, and research from the National Institutes of Health (NIH) shows that abdominal fat (visceral fat) poses greater health risks than fat stored in other areas. For a more complete picture, consider combining BMI with waist circumference measurements and our lean body mass calculator. Learn more about BMI limitations and body fat vs BMI in our detailed guides.
Different populations may need to interpret BMI differently. The WHO has acknowledged that Asian populations may experience elevated health risks at lower BMI values, leading some countries to use a cutoff of 23 (rather than 25) for overweight classification. Similarly, older adults may benefit from slightly higher BMI values, as some research suggests protective effects against frailty and mortality. Our BMI categories guide explains these nuances in detail. Whether you're seeking to lower your BMI or simply understand where you stand, knowledge is the foundation of effective health management. For sex-specific guidance, explore our resources on BMI for women and BMI for men.
Source: CDC National Health and Nutrition Examination Survey (NHANES) 2021-2023
Dive deeper into BMI and weight management with our most popular educational resources:
Everything you need to know about BMI calculations, from basic formulas to advanced interpretation. Includes worked examples in both metric and imperial units.
Learn what constitutes a healthy BMI for your age, sex, and ethnicity. Discover how optimal ranges vary across different populations.
A comprehensive breakdown of all BMI categories from severe underweight to Class III obesity, including health risks associated with each classification.
Women-specific guidance on BMI interpretation, including how hormones, pregnancy, and menopause affect body composition and healthy weight ranges.
Men-specific BMI guidance covering muscle mass considerations, waist circumference thresholds, and how to interpret results for athletic builds.
Evidence-based strategies for achieving a healthier BMI through sustainable lifestyle changes, including diet, exercise, and behavioral modifications.