BMI Chart: What Does It Mean?

Oct 10, 2024

Fact Checked

Learn more about what BMI is and what it could mean for your health.

Edited by: Donya Currie, MA, Senior Editor at NCOA

Medically reviewed by: Amy Beney

Key Takeaways

Body mass index (BMI) is a tool for determining whether a person has a healthy weight-to-height ratio.
Roughly 30.7% of adults in the United States are overweight, 42.4% have obesity, and 9.2% have severe obesity.
A healthy BMI is between 18.5–24.9.
Even though BMI is used as a basis to assess a person’s weight, it isn’t a good representation of health for every person because individual factors are not considered.

Body mass index (BMI) was first created in the 19th century as a surveying tool, but it wasn’t until the early 2000s that it was used to determine a person’s weight health. This is about the time when obesity transformed from a cosmetic concern to a health concern ^[3] . In 2010, physicians started calculating patients’ BMI for annual doctor visits to monitor whether they were at a healthy weight for their height.

While BMI might not be a perfect measurement of a person’s healthy weight, it’s generally seen as a useful screening tool to determine whether they’re an ideal candidate for weight loss management or whether more comprehensive tests are needed to evaluate their health.

What is BMI?

BMI is a value calculated using a person’s height and weight to assess whether or not they’re at a healthy weight. Specifically, BMI is a ratio found by dividing a person’s weight by their height squared ^[4] . It can be calculated using metric or non-metric measurements, with some differences. If you’re using metric, the weight is in kilograms and height in meters. For non-metric use, the weight is in pounds and height in inches.

Here’s how to calculate BMI:

Square your height (multiply the number of meters or inches by itself).
Divide your weight by your height squared.
Multiply that number by 703.
Round to one decimal place.

For example, consider a person who weighs 100 pounds and is 5 feet tall. To calculate their BMI, divide their weight (100 pounds) by their height in inches squared (3,600). Then multiply that number by 703. This person would have a 19.5 BMI.

[100 / (60)²] x 703 = 19.5

That BMI ratio is usually just a pinpoint on a bigger chart that generally ranges from underweight to severe obesity. A person with a high BMI is likelier to have a higher body fat percentage than someone with a lower BMI.

What are the BMI ranges?

BMI is categorized into four different descriptions ranging from underweight to severe obesity ^[5] .

Underweight: Less than 18.5
Healthy weight: 18.5–24.9
Overweight: 25–29.9
Obesity: More than 30

BMI for women

One of the biggest criticisms of the BMI chart is that it’s fixed with only one series of ranges and range descriptions for males and females. This implies that one size fits all, which isn’t necessarily accurate—especially across gender, race, and age.

Women have many biological differences that influence their body composition and can make BMI an inaccurate tool for measuring their health. For example, among women and men with the same BMI, women typically have 10% more body fat than men. That means that even though all people tend to increase body fat as they age, women are still likely to have a higher percentage of fat than men of the same age, height, and weight ^[6] .

According to Jihad Kudsi, MD, an obesity medicine specialist and bariatric surgeon, this is due to “biological factors that prepare the female body for potential pregnancy. Additionally, hormonal fluctuations during menstruation, pregnancy, and menopause can further influence body composition.” Kudsi explained that because “BMI does not directly address variations in body fat distribution or muscle mass, [it] present[s] limitations in accurately assessing health in women.”

BMI for men

The BMI measurement was originally created in the 19th century as a population census tool, which was applied to a sample group of middle-age white males ^[7] . Although this tool was created more than 100 years ago, it still might be able to give a good estimate of weight health for that sample group compared to other groups with different biological dispositions.

“Men typically exhibit higher muscle mass and lower body fat percentages compared to women at equivalent BMI levels. This can sometimes lend BMI a greater degree of accuracy for men due to their muscle-to-fat ratio,” Kudsi said.

Still, men’s body compositions vary based on race, age, and other biological factors. For example, BMI doesn’t differentiate between fat and muscle. “This means individuals with high muscle mass may be classified as overweight or having obesity despite being metabolically healthy,” Kudsi said.

BMI for older adults

Similar to gender disparities, BMI doesn’t account for changes that occur as a person ages. Aging increases bone loss, reduces bone mineral density, and reduces muscle mass ^[8] .

These changes mean that a BMI considered “healthy” for younger people is different for older adults. In fact, many geriatric experts suggest that a BMI range of 31–32 for females and 27–28 for males would be considered healthy for older adults, even though those BMI ranges would be considered “overweight” for adults ages 18–65 ^[9] .

“A slightly higher BMI appears to protect against nutrient deficiencies and osteoporosis,” Kudsi said. For example, studies show that people who were considered moderately overweight (BMI of 26–28) actually have higher bone mineral density than those who are at a healthy weight (BMI of 18.5–24.9) or underweight (BMI less than 18.5). Bones with higher mineral density are stronger and less likely to develop osteoporosis ^[10] . Osteoporosis increases your risk of falls and fractures.

“It’s essential for older adults to focus on overall health rather than solely on BMI. Maintaining muscle mass through strength training and staying active are crucial for healthy aging,” Kudsi said.

BMI Chart

The first step in interpreting a BMI chart is determining your height and weight. If you’re using a chart like the one above with only weight choices for every 10 pounds, just round your weight to the nearest weight available. For example, if you’re 154 pounds, round down to 150. If your height or weight aren’t shown on this chart, try calculating your BMI using the formula in the “What is BMI?” section of this article ([weight in pounds / (height in inches)²] x 703 = BMI).

To use this chart, find your height on the left side. If you’re using a paper version of this chart (printed out), use a highlighter to highlight the row your height is in. If you’re using a digital version of this chart, try to highlight the row with your mouse (left-clicking your mouse and dragging it to the left).

After you find the row for your height, find your weight at the top of the chart. If using a printed version of this chart, highlight the column from your height down. Or, if using a digital version, use your finger to move down the column until you reach the row you highlighted with your mouse.

Your BMI is the number found when the height row and weight column highlights meet.

Benefits of knowing your BMI

Today, we know that obesity is one of the leading causes of diabetes, arthritis, liver disease, several types of cancer, high blood pressure (hypertension), high cholesterol, sleep apnea, and even dementia ^[1] . In the United States, roughly 30.7% of adults are considered overweight, 42.4% have obesity, and 9.2% have severe obesity ^[2] . Even though many experts agree that BMI is an outdated way to assess a person’s overall health, it’s still commonly used as a screening method to determine whether a person is at risk for certain health conditions.

The U.S. Preventive Services Task Force recommends screening for prediabetes and type 2 diabetes in adults ages 35–70 years who are overweight or have obesity ^[11] . Additionally, leading experts recommend people with a BMI higher than 30 have their blood glucose tested every three years to allow earlier detection of type 2 diabetes.

BMI is also used to determine whether weight management surgery or weight management medication is an available option. “A BMI above 35 is often used as a threshold for considering bariatric surgery because, at this level, individuals are at a significantly higher risk of obesity-related health problems, including diabetes, hypertension, sleep apnea, and cardiovascular disease,” said Kudsi.

Faults in BMI

One of the main reasons BMI is so widely used and relied upon to determine weight health is that it’s been around for nearly 180 years and has since been the center of thousands of studies. For example, since 1972, more than 150,000 articles in leading scientific journals have referenced BMI ^[12] . But just because something has been around a long time doesn’t mean it’s the best way to measure health. Various factors aren’t taken into account with BMI.

Most notably, BMI doesn’t differentiate between fat and muscle. One pound of fat weighs the same as 1 pound of muscle. On average, muscle accounts for 40% of a person’s total body weight ^[13] . Consider two people, both 5 feet, 6 inches tall and weighing 150 pounds. Person one is 60% muscle, and person two is only 40% muscle. Both people will have the same BMI but person two has 20% more fat than person one.

BMI also doesn’t take into account a person’s weight distribution. Body fat distribution varies greatly based on body type, and where someone carries fat can indicate higher associated health risks. For example, many health risks associated with obesity are elevated when a person has significant fat accumulation around their vital organs, also called visceral fat ^[14] .

A BMI measurement is based on a person’s height and weight ratio. It doesn’t give any insight into whether the fat is visceral or subcutaneous (the fat stored just beneath the skin). Even a person with a perceived healthy BMI may be at risk for diabetes or cardiovascular disease if they have disproportionate amounts of visceral fat.

Another factor that BMI doesn’t consider is a person’s overall body composition. Each person has a unique bone, muscle, organ, and fat mass. That means not all weights are the same. That’s how people of the same height and weight can look completely different. For example, a person with a broader body build may have a more spread-out weight distribution and look thinner than a person with a narrow build with less surface area to spread their weight.

A BMI measurement cannot calculate many things, some of which can potentially lead to inaccurate determinations about a person’s overall weight health.

Bottom line

While BMI can be a helpful screening tool to get a foundational look at your overall weight health, it’s not the best determinant of your overall health. Due to a person’s biological sex, age, race, and unique body composition, BMI might not give an accurate estimate of their weight profile. If you calculate your BMI and have questions about what that means for your overall health, visit your primary care physician and see if there are other tests that can be done to get a more accurate and comprehensive look at your weight health.

Have questions about this article? Email us at reviewsteam@ncoa.org.

Sources

Shmerling R. How Useful Is the Body Mass Index (BMI)? Harvard Health Publishing. May 5, 2023. Found on the internet at https://www.health.harvard.edu/blog/how-useful-is-the-body-mass-index-bmi-201603309339

National Institute of Diabetes and Digestive and Kidney Diseases. Overweight & Obesity Statistics. September 2021. Found on the internet at https://www.niddk.nih.gov/health-information/health-statistics/overweight-obesity

Flegal KM. Use and Misuse of BMI Categories. AMA Journal of Ethics. July 2023. Found on the internet at https://journalofethics.ama-assn.org/article/use-and-misuse-bmi-categories/2023-07

Centers for Disease Control and Prevention. About Adult BMI. June 2022. Found on the internet at https://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/index.html

National Heart Lung and Blood Institute. Are You at a Healthy Weight? December 2013. Found on the internet at https://www.nhlbi.nih.gov/health/educational/healthdisp/pdf/tipsheets/Are-You-at-a-Healthy-Weight.pdf

Karastergiou K, et al. Sex Differences in Human Adipose Tissues — the Biology of Pear Shape. Biology of Sex Differences. May 31, 2012. Found on the internet at https://bsd.biomedcentral.com/articles/10.1186/2042-6410-3-13
Barrette L. Is BMI Accurate? New Evidence Says No. University of Rochester Medical Center. Jan. 8, 2024. Found on the internet at https://www.urmc.rochester.edu/news/publications/health-matters/is-bmi-accurate

Padilla Colón CJ, et al. Muscle and Bone Mass Loss in the Elderly Population: Advances in Diagnosis and Treatment. Journal of BioMedicine (Syd). November 2018. Found on the internet at http://www.jbiomed.com/v03p0040.htm
Kıskaç M, et al. What Is the Optimal Body Mass Index Range for Older Adults? Annals of Geriatric Medicine and Research. March 25, 2022. Found on the internet at https://www.e-agmr.org/journal/view.php?doi=10.4235/agmr.22.0012

Wu SF and Du XJ. Body Mass Index May Positively Correlate With Bone Mineral Density of Lumbar Vertebra and Femoral Neck in Postmenopausal Females. Medical Science Monitor. Jan. 14, 2016. Found on the internet at https://medscimonit.com/abstract/index/idArt/895512
Davidson K, et al. Screening for Prediabetes and Type 2 Diabetes: US Preventive Services Task Force Recommendation Statement. JAMA. Aug. 24, 2021. Found on the internet at https://pubmed.ncbi.nlm.nih.gov/34427594
Gutin I. In BMI We Trust: Reframing the Body Mass Index as a Measure of Health. Social Theory & Health. Oct. 25, 2017. Found on the internet at https://link.springer.com/article/10.1057/s41285-017-0055-0
Frontera WR and Ochala J. Skeletal Muscle: A Brief Review of Structure and Function. Calcified Tissue International. Oct. 8. 2014. Found on the internet at https://link.springer.com/article/10.1007/s00223-014-9915-y
Cleveland Clinic. Visceral Fat. Sept. 12, 2022. Found on the internet at https://my.clevelandclinic.org/health/diseases/24147-visceral-fat

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