BMI by age group
BMI is read two ways. Adults aged 20 and over use fixed bands. Children and teens aged 2 to 19 use CDC percentiles for their age and sex. This page switches method for you based on the age you enter, and the example is a woman aged 25 at 5 ft 5 in and 140 lb.
How it works
BMI is your weight in kilograms divided by your height in meters squared. From age 20 the page reads the result against the adult bands. For ages 2 to 19 it scores the result against the CDC table for the same age and sex. At 5 ft 5 in the height squared is 2.726.
Worked example
Convert first: 5 ft 5 in is 1.6510 m and 140 lb is 63.5 kg. Then 63.5 ÷ (1.6510 × 1.6510) = 63.5 ÷ 2.726 = 23.3, which is a healthy weight. At age 12 the page would use the CDC table instead.
Median BMI by age from the CDC growth charts, and where the adult bands begin.
| Age | Male median BMI | Female median BMI |
|---|---|---|
| Age 2 | 16.5 | 16.4 |
| Age 3 | 16.0 | 15.7 |
| Age 4 | 15.6 | 15.3 |
| Age 5 | 15.4 | 15.2 |
| Age 6 | 15.4 | 15.2 |
| Age 7 | 15.5 | 15.5 |
| Age 8 | 15.8 | 15.8 |
| Age 9 | 16.2 | 16.3 |
| Age 10 | 16.6 | 16.9 |
| Age 11 | 17.2 | 17.5 |
| Age 12 | 17.8 | 18.1 |
| Age 13 | 18.5 | 18.7 |
| Age 14 | 19.2 | 19.4 |
| Age 15 | 19.9 | 19.9 |
| Age 16 | 20.6 | 20.5 |
| Age 17 | 21.2 | 20.9 |
| Age 18 | 21.9 | 21.3 |
| Age 19 | 22.5 | 21.6 |
| Age 20 | 23.0 | 21.7 |
| Age 20 and over | Adult bands | Adult bands |
Common questions
Which method does this page use at my age?
Ages 2 to 19 use CDC percentiles. Age 20 and over uses the adult bands. For a woman aged 25 at 5 ft 5 in and 140 lb the page uses the adult bands and returns 23.3.
Why do the median BMI values change with age?
BMI falls in early childhood and then rises through the teen years. The male median is 16.5 at age 2, 16.6 at age 10 and 23.0 at age 20.
Where do the adult bands start?
Adult bands begin at age 20. A BMI of 18.5 to 24.9 is a healthy weight, which at 5 ft 5 in is 111 to 150 lb.
Can I use this page for a child under 2?
No. The CDC BMI charts start at age 2, and children under 2 are measured on weight-for-length charts. Ask your child's doctor.
Does the page work for older adults?
Yes. At age 80 the same formula applies. A height of 5 ft 5 in and a weight of 140 lb still give 23.3.