CDC BMI Categories for Adults (with Calculator)

CDC adult BMI categories chart

These are the CDC's categories and ranges, word for word. BMI is measured in kg/m².

The CDC also groups the three classes together as Obesity: a BMI of 30 or greater. The categories are the same for men and women and do not change with age once you are 20 — in the CDC's words, they are "based on a person's BMI regardless of age, sex, or race."

Using NHS ranges instead? See the NHS BMI categories.

What each category means

Underweight — less than 18.5

A low BMI can reflect a naturally slim build, but it can also go with poor nutrition or an illness that causes weight loss. If your BMI is under 18.5 and you are not sure why, or you are losing weight without trying, it is worth speaking to a doctor.

Healthy Weight — 18.5 to less than 25

This is the range the CDC labels healthy for adults. It is a population guide rather than a personal target: someone at 24 with a lot of muscle and someone at 24 with little activity can have quite different health.

Overweight — 25 to less than 30

Overweight sits between Healthy Weight and the obesity classes. The higher your BMI climbs, the more likely weight-related conditions such as type 2 diabetes and high blood pressure become, so this range is a common point to look at diet, activity and waist size.

Class 1, 2 and 3 Obesity — 30 and above

The CDC splits obesity into Class 1 (30 to less than 35), Class 2 (35 to less than 40) and Class 3 (40 or greater), which it also calls severe obesity. The classes help doctors talk about how much weight is involved; what support makes sense depends on your wider health, not BMI alone.

Healthy weight for your height

A healthy BMI of 18.5 to less than 25 works out to these weights. Figures are rounded inwards, so every weight shown is inside the range.

Example: every category at 5′9″

For an adult who is 5 feet 9 inches tall, these weights fall into each CDC category:

How BMI is calculated

BMI is your weight divided by your height squared:

Metric:  BMI = weight (kg) ÷ height (m)²
Imperial: BMI = weight (lb) ÷ height (in)² × 703

For example, 180 lb at 5′8″ (68 inches) gives 180 ÷ 68² × 703 = 27.4, which is Overweight. In metric, 82 kg at 1.73 m gives 82 ÷ 1.73² = 27.4. The calculator above does the conversion exactly, so its answer can differ from the 703 shortcut in the second decimal place.

When BMI can be misleading

BMI is a quick screening number, not a diagnosis. It can give the wrong impression when:

• You carry a lot of muscle. BMI cannot tell muscle from fat, so athletes and people who do heavy strength training can land in Overweight or even Obesity with little body fat.
• Fat sits around your middle. Two people with the same BMI can carry fat very differently. The NHS suggests keeping your waist to less than half your height as an extra check.
• You are pregnant, or a condition affects your height. The NHS advises not using an adult BMI calculator in these cases.
• Your family background is South Asian, Chinese, other Asian, Middle Eastern, Black African or African-Caribbean. The NHS says health risks start at a slightly lower BMI for these groups and uses lower cut-offs. The CDC's adult categories are the same for everyone.
• You are under 20. Adult categories don't apply; the CDC uses BMI-for-age percentiles for ages 2 through 19 (Child and Teen BMI Calculator). Our Child & Teen BMI Percentile Calculator uses the same CDC data.

If your result surprises you, or you have been diagnosed with an eating disorder or think you may have one, talk to a doctor rather than relying on the number.

CDC vs NHS categories

The main cut-offs match, but the two systems differ in who they cover and how they label the top of the scale:

To check your BMI against the NHS ranges, switch the BMI calculator to NHS mode.

Frequently asked questions