Using body mass index (BMI) is one way a person can determine whether or not their weight is healthy for them. BMI takes both height and weight into consideration.

Carrying too much or too little weight can increase a person’s risk of health problems, either in the present or the future.

A person’s BMI is not the only factor that affects this risk. Other tools for assessing whether or not a person has a healthy weight or body composition for them include waist-to-hip ratio, waist-to-height ratio, and body fat percentage.

However, BMI is a useful starting point. This article provides some tools for people to work out their BMI.

## BMI calculators

These calculators and charts can give an indication of whether or not a person’s weight may affect their risk of health problems.

This article publishes the calculators courtesy of The Calculator Site. There are two calculation options available: metric and imperial.

## BMI charts

To use the charts below, a person can find their weight in pounds along the top and their height in feet and inches down the side. They can then look across to find their BMI.

There are two charts. If a person’s weight is 245 pounds (lb) or under, they should use the first chart. If their weight is over 250 lb, they should look at the second one.

The shaded areas correspond to BMI values that indicate either a moderate weight, overweight, or obesity.

In addition, researchers and doctors divide obesity into three categories:

• Class 1: BMI is 30–34.9.
• Class 2: BMI is 35–39.9.
• Class 3: BMI is 40 and above.

The charts are an adaptation of the adult BMI chart created by the University of Vermont in Burlington.

### BMI chart: Weight of 95–245 lb

Adult BMI chart showing ranges “under healthy weight: BMI < 18.5,” “healthy weight: BMI 18.5–24.9,” and “overweight: BMI 25–29.9.”

### BMI chart: Weight of 250–400 lb

Adult BMI chart showing ranges “obese 1: BMI 30–34.9,” “obese 2: BMI 35–39.9,” and “obese 3: BMI ≥ 40.”

These figures are only a guide. The BMI tools do not determine whether or not a person has an ideal body weight, but they can help show if an individual’s weight may increase their risk of disease.

A person who is very fit, such as an Olympic athlete, may have a high BMI. However, this does not necessarily mean that they are overweight due to excess body fat. The excess weight, in that case, may be due to increased muscle mass.

## BMI categories

The following table shows the standard weight status categories associated with BMI ranges for adults:

 Below 18.5 Underweight 18.5–24.9 Healthy 25–29.9 Overweight 30 and above Obese
BMI of under 18.5

A BMI of under 18.5 indicates that a person has insufficient weight, so they may need to put on some weight. They should ask a doctor or dietitian for advice.

BMI of 18.5–24.9

A BMI of 18.5–24.9 indicates that a person has a healthy weight for their height. By maintaining a healthy weight, they can lower their risk of developing serious health problems.

BMI of 25–29.9

A BMI of 25–29.9 indicates that a person is slightly overweight. A doctor may advise them to lose some weight for health reasons. They should talk with a doctor or dietitian for advice.

BMI of over 30

A BMI of over 30 indicates that a person has obesity. Their health may be at risk if they do not lose weight. They should talk with a doctor or dietitian for advice.

## Health risks

Maintaining a moderate weight can help prevent a range of health conditions.

People who are overweight may have a higher risk than others of conditions such as heart disease, type 2 diabetes, sleep apnea, and colorectal cancer. Some of these can be life threatening.

Having insufficient weight can increase the risk of malnutrition, osteoporosis, anemia, and a range of problems that can result from various nutrient deficiencies. It can also be a symptom of a hormonal, digestive, or other problem.

## Varying cutoff points

Some evidence suggests that the associations between BMI, body fat percentage, and body fat distribution may differ across populations due to variations in sex, race, and ethnicity.

A Brazilian study from 2017 looked at the correlation between BMI and body fat percentage in 856 adult males and females.

They concluded that to predict obesity-type body fat percentage, the standard BMI threshold of 29.9 kilograms per square meter (kg/m2) was appropriate for males but that a more suitable cutoff point for females appeared to be 24.9 kg/m2.

In 2017, Korean researchers pointed out that people in the Asia-Pacific region often have a higher risk of type 2 diabetes and cardiovascular disease at a BMI below the existing World Health Organization (WHO) cutoff point of 25 kg/m2.

In Korea, they added, there is evidence to suggest that almost twice as many people have features of metabolic obesity but a moderate weight compared with the United States.

The results of one 2011 study found that Asian American people within the healthy weight range were more likely to have symptoms of metabolic syndrome than their non-Hispanic white counterparts.

The following table by the WHO shows some comparisons and cutoff points that may apply. Doctors may use these variations when advising or treating conditions in specific people.

 Underweight < 18.50 < 18.50 Severe thinness < 16 < 16 Moderate thinness 16–16.99 16–16.99 Mild thinness 17–18.49 17–18.49 Normal range 18.5–24.99 18.5–22.9923–24.99 Overweight ≥ 25 ≥ 25 Pre-obese 25–29.99 25–27.4927.5–29.99 Obese ≥ 30 ≥ 30 Obese class 1 30–34.99 30–32.4932.5–34.99 Obese class 2 35–39.99 35–37.4937.5–39.99 Obese class 3 ≥ 40 ≥ 40

To discover more evidence-based information and resources for obesity & weight management, visit our dedicated hub.

## Summary

BMI is a useful tool that gives a general idea about whether or not a person’s weight is healthy for them.

However, it is a simple tool that does not tell the whole story about people’s individual weight and health risks.

Anyone who is concerned about their weight should speak with a doctor, who may also consider their body fat distribution and the ratio of their waist size to their height. The doctor will also be able to offer advice to suit every individual.