Your body mass index (BMI) is an approximate calculation of your body mass, which is used to predict your amount of body fat based on your height and weight. BMI numbers range from low to high and fall into several categories:
- <19: underweight
- 19 to 24: normal
- 25 to 29: overweight
- 30 to 39: obese
- 40 or above: extreme (morbid) obesity
Having a higher BMI number increases your risk of serious health conditions, including:
- heart disease
- high blood pressure
- high cholesterol
- type 2 diabetes
- breathing problems
- certain kinds of cancer
You can calculate your own BMI on the Centers for Disease Control and Prevention website.
Here’s a look at a BMI chart. Follow these steps to read the chart:
- Find your height (inches) in the left-hand column.
- Scan across the row to find your weight (pounds).
- Scan upward to the top of the column to find the corresponding BMI number for that height and weight.
For example, the BMI for a person 67 inches tall weighing 153 pounds is 24.
Note that the BMI numbers in this table range from 19 to 30. For a BMI chart showing numbers greater than 30,
It’s helpful that BMI numbers are standardized and offer ranges of healthy body weights. But it’s only one measure and doesn’t tell the whole story.
For example, BMI doesn’t take into consideration your age, sex, or muscle mass, which are all important when it comes to finding your ideal weight.
Older adults tend to lose muscle and bone, so more of their body weight is likely to come from fat. Younger people and athletes may weigh more due to strong muscles and denser bones. These realities can skew your BMI number and make it less accurate for predicting exact body fat levels.
The same goes for women, who tend to carry more body fat, versus men, who tend to have more muscle mass. So, a man and woman with the same height and weight will get the same BMI number but may not have the same body fat-to-muscle ratio.
“As we age, unless we are exercising, we will lose lean tissue mass (usually muscle, but also bone and organ weight) and gain fat. Females have more fat mass than males. If you have more muscle, your BMI may categorize you as overweight or obese,” says Dr. Naomi Parrella, medical director for the Center for Weight Loss and Lifestyle Medicine at Rush University.
More than strictly how much you weigh, body composition and where you store fat can have great impact on your overall health. People who store more body fat around their waist have an increased risk of health problems compared to people who store body fat around their hips. For this reason, it’s helpful to calculate your waist-to-hip (WHR) ratio.
Ideally, your waist should have a smaller circumference than your hips. The greater your WHR is, the higher the risk for related health issues.
A WHR ratio above 0.90 in males and 0.85 in females is considered abdominal obesity, according to the World Health Organization (WHO). Once a person reaches this point, they are considered to have a substantially increased risk for associated medical problems.
Some experts believe WHR ratio might be more accurate than BMI for assessing health risks. A 2015 study of more than 15,000 adults found that people with a normal BMI but a high WHR were still more likely to die early. This was especially true for men.
The results mean that a man who has a normal BMI can have excess weight around their waist that drastically increases their risk of health problems.
The study only found correlation between WHR ratios and early death. It didn’t examine exactly why excess abdominal fat could be deadlier. A high WHR ratio might suggest urgent need for diet and lifestyle improvement.
That said, the WHR ratio is not a good tool for everyone, including children, pregnant women, and people who are shorter than average.
Measuring your waist-to-height ratio is another way to see measure excess fat around the middle.
If your waist measurement is more than half of your height, you may be at increased risk of obesity-related illness such as cardiovascular problems and early death. For example, a 6-foot-tall person would ideally have a waist that’s less than 36 inches with this ratio.
A small 2017 study of adult men and women found that waist-to-height ratio might be a better indicator of obesity than BMI. More research is needed to compare larger numbers of people including more diversity in age and ethnicity.
Since the real concern about body weight is actually about unhealthy levels of body fat, it might be best to try calculating your body fat percentage. There are a variety of ways to do this, but the best way is to work with a doctor.
You can use at-home tools to try to determine your body fat percentage, but doctors have more accurate methods. There are also some calculations that use information such as your BMI and your age to find a body fat percentage, but they’re not consistently accurate.
Keep in mind that fat under the skin (referred to as baby fat or a general softness to the body) is not as worrisome. The more troublesome body fat is stored around your organs.
It may cause increased pressure, leading to inflammation in the body. For this reason, waist measurements and body shape may be the simplest and most helpful elements to track.
Waist and body shape
We don’t know why, but studies show excess belly fat is more dangerous than fat distributed more evenly throughout the body. One theory is that all of the vital organs in your core are affected by the presence of too much belly fat.
Genetics influences where and how people store body fat. While that’s not something we can control, it’s still a good idea to practice healthy eating and exercise as much as possible.
In general, men are more likely to develop body fat around the waist and have higher waist measurements. But as women age and especially after menopause, hormones cause them to start adding more weight around their waist.
For this reason, it may be best to pay attention to how your clothing fits, rather than checking the scale, says Parrella. “Waist measurement is the most important for assessing risk.”
There’s no perfect way to determine your ideal weight, as it depends on many factors. Those factors include not only your body fat percentage and distribution, but also your age and sex.
“Depending on the weight someone is starting at, ‘ideal’ may have many meanings. Five to 10 percent weight loss in a person is medically significant, and can improve health risks,” says Parrella.
Also, things like pregnancy can make your bones and muscles heavier and denser to accommodate for the extra weight. In these cases, a healthy weight for you may be higher than you expect to account for the healthy muscle and bone density that you gained.
If you’re concerned with overall fitness and quality of life, talk with your doctor about starting a diet and exercise program.
“Your body will settle down at a weight that’s best for you, if you have a healthy lifestyle,” says Parrella.