A BMI of 18.5 to 24.9 is a healthy weight, 25.0 to 29.9 is overweight, 30.0 or above is obesity, and below 18.5 is underweight, according to the CDC categories for adults aged 20 and over. BMI is a screening tool, not a diagnosis, so your number is a starting point, not a verdict on its own.
A BMI chart turns a single number into a category, and each category carries a different average health risk. But the chart is widely misunderstood: people treat the boundaries as sharp lines, assume the same ranges apply to children, or read a result of 25.5 as a diagnosis. This guide explains the full chart, what each category means, how the three obesity classes differ, and how to find your own healthy weight range, using the CDC adult categories.
The BMI Categories Chart
The CDC defines four adult BMI categories for adults aged 20 and over. They are the same for men and women, and do not change with age within adulthood.
| BMI | Category | What it means |
|---|---|---|
| Below 18.5 | Underweight | Below the healthy weight range for your height |
| 18.5–24.9 | Healthy weight | Within the range linked to the lowest average health risk |
| 25.0–29.9 | Overweight | Above the healthy weight range for your height |
| 30.0 and above | Obesity | Well above the healthy weight range, with higher average risk |
The boundaries are exact to one decimal place: 24.9 is healthy weight, while 25.0 is overweight. BMI is calculated as weight in kilograms divided by height in metres squared, or (weight in pounds × 703) divided by height in inches squared. A result within 0.5 points of a boundary should be treated as borderline.
What Does Underweight Mean? (Below 18.5)
A BMI below 18.5 is classed as underweight: body weight below the range associated with the lowest average health risk for your height. Causes include a naturally slight build, a recent illness, a reduced appetite, an overactive thyroid, a digestive condition, or an eating disorder, and in older adults, muscle loss. Being underweight is linked to higher risk of nutritional deficiency, weakened immunity, anaemia, and bone loss, including osteoporosis and fractures. A BMI below 18.5 is a reason to check nutrition and talk to a clinician, especially if the low weight is new.
What Does Healthy Weight Mean? (18.5–24.9)
A BMI of 18.5 to 24.9 is classed as healthy weight. Across large population studies, adults in this range have, on average, the lowest risk of conditions such as type 2 diabetes, heart disease, high blood pressure, and certain cancers. That is why the range is called healthy: it is the band where average risk is lowest, not a guarantee of health for any one person.
Healthy weight is a range, not a single ideal number. At 1.75 metres, it spans roughly 57 to 76 kilograms, and at 5 feet 9 inches, 125 to 169 pounds. A healthy BMI does not by itself prove good health: a person can have a BMI of 22.0 and still have high blood pressure or low fitness.
What Does Overweight Mean? (25.0–29.9)
A BMI of 25.0 to 29.9 is classed as overweight. In the United States, more than 1 in 3 adults fall in this range. Risk of type 2 diabetes, heart disease, high blood pressure, and osteoarthritis rises gradually across the range: the risk at 25.5 is only slightly above the risk at 24.5, while the risk at 29.5 is noticeably higher. A waist above 40 inches (102 cm) for men or 35 inches (88 cm) for women adds risk, because fat around the waist is more closely linked to disease than fat stored elsewhere.
Overweight is a screening category, not a disease and not a judgement. For example, a person who is 1.75 metres tall and weighs 78 kilograms has a BMI of 78 ÷ (1.75 × 1.75) = 78 ÷ 3.0625 = 25.5, which is overweight. The same person at 70 kilograms has a BMI of 70 ÷ 3.0625 = 22.9, a healthy weight. Small, sustained changes in eating and activity can move a borderline result back into the healthy range over months.
What Does Obesity Mean? (30.0 and Above)
A BMI of 30.0 or above is classed as obesity. It is divided into three classes, because risk rises steeply as BMI climbs above 30, and the classes help clinicians judge which treatments are appropriate.
Obesity Class 1: BMI 30.0–34.9
Class 1 is the mildest obesity class, but it still carries a clearly higher average risk than the overweight range. The risk of type 2 diabetes, heart disease, high blood pressure, sleep apnoea, and joint problems is elevated, and rises from 30.0 to 34.9. Most people in Class 1 start with structured lifestyle change before medication is considered.
Obesity Class 2: BMI 35.0–39.9
Class 2, sometimes called moderate obesity, carries a substantially higher risk than Class 1. Type 2 diabetes, heart disease, stroke, sleep apnoea, and fatty liver disease are all more common, and mobility and joint pain often become limiting. Clinicians may discuss medication alongside lifestyle change.
Obesity Class 3: BMI 40.0 and Above
Class 3, sometimes called severe obesity, carries the highest average risk. At a BMI of 40.0 or above, the risk of type 2 diabetes, heart disease, stroke, sleep apnoea, and several cancers is several times higher than in the healthy range, and life expectancy is reduced on average. Clinicians may discuss medication and, in some cases, bariatric surgery, alongside intensive lifestyle support.
Obesity classes at a glance
| Class | BMI range | Typical clinical approach |
|---|---|---|
| Class 1 | 30.0–34.9 | Lifestyle change first; medication if other conditions are present |
| Class 2 | 35.0–39.9 | Lifestyle change plus medication often discussed |
| Class 3 | 40.0 and above | Full range of treatments, including medication and possibly surgery |
What Is Your Healthy Weight Range?
A BMI chart tells you the category, but most people want the answer in kilograms or pounds: what weight range is healthy for my height? Find it with one formula, the BMI calculation in reverse: Weight = BMI × height². Use 18.5 for the lower end and 24.9 for the upper end, in metric units (kilograms and metres) or imperial units (pounds and inches).
Worked example: 5 feet 9 inches
A person who is 5 feet 9 inches tall is 69 inches tall, which is 1.75 metres.
- Lower end: 18.5 × (1.75 × 1.75) = 18.5 × 3.0625 = 56.7 kilograms, about 125 pounds.
- Upper end: 24.9 × (1.75 × 1.75) = 24.9 × 3.0625 = 76.3 kilograms, about 169 pounds.
So the healthy weight range for 5 feet 9 inches is 125 to 169 pounds (about 57 to 76 kilograms), a span of 44 pounds. At 150 pounds and 5 feet 9 inches, BMI is (150 × 703) ÷ (69 × 69) = 105,450 ÷ 4,761 = 22.2, comfortably inside the healthy range. Find your own range with the free body mass index calculator on Calcrio.
Healthy weight range by height
| Height | Healthy weight range |
|---|---|
| 5 ft 0 in (152 cm) | 94–127 lb (43–58 kg) |
| 5 ft 6 in (168 cm) | 115–155 lb (52–70 kg) |
| 5 ft 9 in (175 cm) | 125–169 lb (57–76 kg) |
| 6 ft 0 in (183 cm) | 137–184 lb (62–83 kg) |
These ranges come from the same formula — BMI 18.5 to 24.9 multiplied by height squared — for adults aged 20 and over. If your height is not in the table, use the formula above, or check a BMI calculator.
Who Do the BMI Categories Apply To?
The CDC adult categories apply to adults aged 20 and over, and are the same for men and women at every adult age. That simplicity is a strength for population screening and a limitation for individuals, because body composition changes with age and differs between men and women, yet the cutoffs do not adjust for either.
The categories do not apply to children and teenagers aged 2 to 19. For that age group, the CDC uses BMI-for-age percentiles: a BMI-for-age at or above the 85th percentile is classed as overweight, and at or above the 95th percentile as obesity. The categories are also less reliable for some adults: very muscular people, including athletes, can have a BMI above 25.0 while carrying little body fat; older adults may have a healthy BMI while carrying a high proportion of body fat; and people of some ethnic backgrounds, including South Asian, Chinese, and Japanese populations, face higher diabetes risk at a given BMI. Pregnant people should not use the standard chart at all.
FAQ: BMI Categories Chart
What BMI is considered healthy?
For adults aged 20 and over, a healthy BMI is 18.5 to 24.9, according to the CDC. Below 18.5 is underweight, 25.0 to 29.9 is overweight, and 30.0 or above is obesity.
What are the 3 classes of obesity?
Class 1 is a BMI of 30.0 to 34.9, Class 2 is 35.0 to 39.9, and Class 3, sometimes called severe obesity, is 40.0 or above. Health risk rises across the classes, and Class 1 is usually managed with lifestyle change first.
What is the healthy weight range for 5 ft 9 in?
The healthy weight range for 5 feet 9 inches is 125 to 169 pounds, or about 57 to 76 kilograms. It comes from weight = BMI × height squared, using BMI 18.5 and 24.9. At 150 pounds, BMI is 22.2, inside the healthy range.
Is a BMI of 25.5 overweight?
Yes. A BMI of 25.5 falls in the overweight range of 25.0 to 29.9. It is only just above the healthy range, so read it as borderline. It is a prompt to check waist circumference and blood pressure, not a diagnosis.
Do BMI categories apply to children?
No. Children and teenagers aged 2 to 19 use CDC BMI-for-age percentiles, not the adult cutoffs. At or above the 85th percentile is overweight, and at or above the 95th percentile is obesity.
Is BMI a diagnosis?
No. BMI is a screening tool, not a diagnosis. It does not distinguish muscle from fat, and does not account for age, sex, or ethnicity. A BMI outside the healthy range means a fuller health check is worth doing.