Height-for-age and weight-for-age from the CDC growth charts
Updated October 2026
The CDC growth charts give L (skew), M (median) and S (spread) for every half month from 24 to 240 months. The calculator interpolates them for the child’s exact age, converts the measurement to a z-score with z = ((X ÷ M)L − 1) ÷ (L × S), and reports the percentile below that z-score.
At exactly 8 years (96 months), boys’ stature values are L = 0.4634, M = 127.88 cm and S = 0.04509. A height of 50.4 in is 128.02 cm, giving z = 0.024, the 51st percentile. Weight uses its own table (median 25.64 kg, or 56.5 lb), and 56.9 lb comes out at z = 0.042, the 52nd percentile.
Because the median keeps rising, a fixed height slides down the chart as a child gets older. A boy who stays 50.4 inches tall:
| Age | Median height for boys | Percentile for 50.4 in |
|---|---|---|
| 6 years | 45.4 in | 99th |
| 7 years | 47.9 in | 87th |
| 8 years | 50.3 in | 51st |
| 9 years | 52.6 in | 18th |
| 10 years | 54.6 in | 5th |
That is why a stall in height shows up as falling percentiles even when nothing is measured wrong.
| Age | Boys, height | Girls, height | Boys, weight | Girls, weight |
|---|---|---|---|---|
| 2 | 34.2 in | 33.6 in | 28.1 lb | 26.8 lb |
| 4 | 40.2 in | 39.7 in | 35.8 lb | 34.8 lb |
| 6 | 45.4 in | 45.2 in | 45.6 lb | 44.6 lb |
| 8 | 50.3 in | 50.2 in | 56.5 lb | 56.5 lb |
| 10 | 54.6 in | 54.3 in | 70.4 lb | 72.5 lb |
| 12 | 58.7 in | 59.5 in | 89.2 lb | 91.8 lb |
| 14 | 64.5 in | 63.1 in | 112.4 lb | 108.8 lb |
| 16 | 68.3 in | 64.0 in | 134.3 lb | 118.8 lb |
| 18 | 69.4 in | 64.2 in | 148.1 lb | 123.9 lb |
Enter age as years plus months (a child who turned 8 three months ago is 8 years, 3 months); from age 2 no prematurity correction is applied. Measure height standing, without shoes, heels against a wall, looking straight ahead, with a flat object resting on the head. Weigh in light clothing. Either measurement can be left at 0. With both, the calculator also shows BMI; use the child BMI calculator for its percentile, which is how weight status is judged.
| Measure | Cutoff | What it prompts |
|---|---|---|
| Height-for-age | Below the 3rd percentile (about −2 SD) | Defined as short stature; evaluation looks at growth rate, parents’ heights and bone age |
| Height-for-age | Above the 97th percentile | Defined as tall stature; usually familial |
| BMI-for-age | Under the 5th percentile | Underweight |
| BMI-for-age | 5th to under 85th | Healthy weight |
| BMI-for-age | 85th to under 95th | Overweight |
| BMI-for-age | 95th or above; severe at 120% of the 95th or BMI 35+ | Obesity |
The stature definitions come from the American Academy of Family Physicians’ 2015 review; the BMI categories are the CDC’s for ages 2 through 19 (page updated June 2024). The CDC has recommended its growth charts for ages 2 and up since its 2010 guidance, and the charts themselves date from 2000.
Treating the 50th percentile as the goal. A child following the 20th percentile with short parents is usually growing normally. Reading weight-for-age as a weight-status check. A tall child will have a high weight percentile at a healthy BMI. Mixing charts at age 2. Switching from WHO to CDC can move a percentile by itself, because the reference groups differ. Comparing shoes-on and shoes-off heights adds the heel to one of them. Reading one percentile change during puberty as a problem. Early and late developers move across lines temporarily, and teens can still be growing at 17 or 18.
It does not assess growth rate, puberty stage, nutrition or any medical condition, and a percentile is not a diagnosis. Most children outside the usual range are healthy variants of normal; the AAFP review notes that children more than three standard deviations from the mean are more likely to have an underlying cause. Talk with your child’s pediatrician if height is below the 3rd or above the 97th percentile, if height or weight crosses two major percentile lines, if growth seems to have stopped for months, or if puberty starts much earlier or later than in classmates. Bring past measurements; the pediatrician plots the trend, which says more than any single visit.