Beginners What Is Body Mass Index (BMI) and What Does It Measure? By Elizabeth Quinn Elizabeth Quinn is an exercise physiologist, sports medicine writer, and fitness consultant for corporate wellness and rehabilitation clinics. Learn about our editorial process Elizabeth Quinn Reviewed by Reviewed by Marisa Moore, RDN, MBA on January 27, 2020 pinterest instagram Marisa Moore is a registered dietitian nutritionist with a BS in nutrition science and MBA in marketing. She is also the founder of Marisa Moore Nutrition. Learn about our Review Board Marisa Moore, RDN, MBA Updated on February 12, 2020 Print Table of Contents View All How BMI Is Measured Other Measurement Methods Limitations to BMI Health Risks of High BMI BMI, which stands for body mass index, is a calculation that is sometimes used in healthcare settings as an indirect method to determine a person's body fat category. This BMI calculator can help you learn what this measurement means and how it relates to your health and fitness. BMI is not a diagnostic tool nor is it a measurement of body fat percentage. A high BMI may be an indicator of high body fatness, but it doesn't necessarily mean that a person is overweight or obese and it is not a direct indicator of health. In some populations, BMI has been found to be a fairly reliable indicator of body fat measures. But the calculation is less effective in other groups, such as bodybuilders and the elderly. There are other methods that are more accurate in estimating body fat. How BMI Is Measured Your BMI is calculated using your height and weight. It can be a starting point for understanding the way your body fat may impact your overall health. You can use the number along with other health measurements to begin a conversation with your healthcare provider about ways to reduce your risk for disease and improve your overall wellness. Metric BMI Formula: weight (kg) / [height (m)]2Example: weight = 68 kg, height = 165 cm (1.65 m)BMI calculation: 68 / (1.65)2 = 24.98 English BMI Formula: weight (lb) / [height (in)]2 x 703Example: weight = 150 lbs, height = 5’5” (65")BMI calculation: [150 / (65)2] x 703 = 24.96 What Your Result Means For adults, BMI results are interpreted as follows:BMI below 18.5 = UnderweightBMI 18.5 – 24.9 = Normal weightBMI 25.0 – 29.9 = OverweightBMI 30.0 and above = Obese Note that BMI is interpreted differently in children. Growth charts and percentiles are used. If children are at or above the 95th percentile of children their age, they are considered obese. Other Body Fat Measurement Methods There are several methods of assessing the percent of fat and lean mass of an individual. These methods are referred to as body composition analysis. Some of the most common measurements include: Underwater weighing: This procedure, also called hydrodensitometry, is complex and complicated, so it is rarely used.Skinfold thickness measurements: Many experts use this simple method to determine body composition.Bioelectrical impedance: This common method of assessing body fat percentage determines total body weight, the percent and amount of body fat, muscle mass, water, and even bone mass. While readings can be affected by hydration level and other factors, they provide fairly accurate results over time. Some body fat scales for home use employ this method of measurement. Limitations to BMI Even though there is a fairly strong correlation between BMI and body fat measurement, there are some limitations based on an individual's gender, age, and athletic ability. Women tend to have more body fat than men, and older people tend to have more body fat than younger people. Highly trained athletes often have a high BMI due to higher levels of muscle mass, which increases their body weight measurement. Body Composition, Body Fat, and BMI Athletes who have higher levels of muscle mass need to be leery of the BMI calculation. Because the BMI number cannot distinguish the different components that make up total body weight, an athlete is better served by using a direct measurement of body composition and body fat. The BMI calculation is used to screen the general population for health risks related to having too much body fat. This tool does not work well for most athletes who are curious about their body composition. Health Risks Related to High BMI The reason BMI is used for screening the health of the general population is due to the correlation between being overweight or obese and having certain health problems. People who are overweight or obese have an increased risk for: HypertensionSleep apnea and respiratory problemsType 2 diabetesCoronary heart diseaseStrokeOsteoarthritisSome cancers It is important to understand, however, that body fatness is not the only predictor of health. Researchers are trying to understand the "obesity paradox." Specifically, experts have found that despite the potential adverse impact of overweight and obesity, evidence demonstrates that being overweight or mildly obese is associated with improved survival. Fitness is also important. Researchers have found that being fit negates the adverse effects of body fatness, as well as other traditional cardiovascular risk factors, including overweight/obesity, metabolic syndrome, type 2 diabetes mellitus, and hypertension. A Word From Verywell While body mass index can be a useful tool for some people, it is just one number that should be balanced out with other evidence. Talk to your healthcare provider about the best way to understand your BMI as part of a comprehensive plan for good health and longevity. Was this page helpful? Thanks for your feedback! Get exercise tips to make your workouts less work and more fun. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit Article Sources Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy. Centers for Disease Control and Prevention. About adult BMI. Updated April 10, 2020. National Institute of Diabetes and Digestive and Kidney Diseases. Health risks of overweight and obesity. Updated February 2018. Lavie CJ, McAuley PA, Church TS, Milani RV, Blair SN. Obesity and cardiovascular diseases: implications regarding fitness, fatness, and severity in the obesity paradox. J Am Coll Cardiol. 2014;63(14):1345-54. doi:10.1016/j.jacc.2014.01.022