# What is my child’s height percentile?

Finds a child’s height-for-age (or length-for-age) percentile and z-score from birth to 20 years, on the WHO growth standards under 24 months and the CDC growth charts from 2 years.

- Page: https://www.acalculator.org/health/height-percentile-calculator
- JSON spec: https://www.acalculator.org/health/height-percentile-calculator.json
- Version: c45a2a1d7841

## Default answer

Example with the default inputs (Sex Boy, Based on Age, Years 4, Months 0, Height 40.5 in) on the example date Wednesday, September 30, 2026: At 4 years, a height of 40.5 in is at percentile 56.1 on the CDC stature-for-age (2 to 20 years) chart.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| sex | Sex | The child’s sex. Boys and girls have separate growth charts. |
| from | Based on | Enter the age in years and months, or the birth date and the date of the measurement. |
| years | Years | The age in whole years. |
| months | Months | Months past the whole years, 0 to under 12. Decimals are allowed: 2 weeks is about 0.5. |
| born | Birth date | The child’s date of birth. |
| on | Measured on | The date of the measurement. Today, unless you change it. |
| height | Height | The child’s height without shoes; under 2 years, the length measured lying down. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| percentile | Height percentile | The share of children of the same sex and age who are shorter, rounded to one decimal place and shown between 0.1 and 99.9. |
| z | Z-score | How many standard deviations the height is above (+) or below (−) the median for the age. |
| median | Median height at this age | The 50th percentile height for the sex and age. |
| low | 5th percentile height | The height at the 5th percentile for the sex and age. |
| high | 95th percentile height | The height at the 95th percentile for the sex and age. |
| range | Screening range | Where the percentile falls against the screening cut-offs: 2.3rd and 97.7th on the WHO charts, 5th and 95th on the CDC charts. |
| age | Age | The child’s age in years and months. |
| chart | Growth chart | The growth chart used for this age. |

## Method

z = ((height ÷ M)^L − 1) ÷ (L × S), height in cm; percentile = Φ(z) × 100, with L, M and S for the sex and age from the WHO length table under 24 months and the CDC stature table from 24 months, read on a straight line between table ages.

## Assumptions

- Under 24 months the page uses the WHO 2006 length-for-age standard (measured lying down); from 24 months to 20 years, the CDC 2000 stature-for-age chart (measured standing), as the CDC advises for US children.
- Age in months is 12 × years + months, or the days from birth to the measurement ÷ 30.4375.
- The percentile is rounded half up to one decimal place and shown between 0.1 and 99.9.
- A percentile compares a child with a reference group. It is not a diagnosis; a doctor looks at growth over time.

## Worked examples

1. sex = female, from = age, years = 1, months = 0, height = 0.79165 gives percentile = 97.7, z = 2, median = 0.74015, low = 0.697795, high = 0.782505, range = Between the 2.3rd and 97.7th percentiles, chart = WHO length-for-age (birth to 24 months). Source: WHO length-for-age, girls, month 12 (CDC copy of the WHO table): L 1, M 74.015, S 0.03479.
2. sex = male, from = age, years = 12, months = 6.5, height = 1.475269 gives percentile = 25, z = -0.67449, median = 1.526624, low = 1.402831, high = 1.655302, chart = CDC stature-for-age (2 to 20 years). Source: CDC statage.csv, boys, 150.5 months: L 0.531951655, M 152.6623878, S 0.050273285, P25 147.5268957 cm.
3. sex = female, from = age, years = 12, months = 0, height = 1.524 gives percentile = 56.5, z = 0.164269, age = 12 years. Source: CDC statage.csv, girls, 144 months (between the 143.5 and 144.5 rows): a 5 ft (152.4 cm) girl.

## FAQ

### What does a height percentile mean?

It is the share of children of the same sex and age in the reference group who are shorter. A girl at the 40th percentile is taller than 40 of every 100 girls her age on the chart.

### Why is a baby’s length used instead of height?

Under 2 years, children are measured lying down (length), and the WHO length-for-age standard uses those measurements. From 2 years, the CDC stature-for-age chart uses standing height. A child is usually about 0.7 cm (0.3 in) shorter standing than lying down, so the switch at 24 months can move the percentile a little.

### What is a normal height percentile?

Children of healthy height can be at any percentile. What matters most is a steady pattern over time. For screening, the CDC suggests the 2.3rd and 97.7th percentiles on the WHO charts and the 5th and 95th on the CDC charts. A doctor may look more closely at a child outside those, or one who crosses percentile lines.

### Can I use this for adults?

No. The charts end at 20 years. Adult heights are compared with national survey data, not with growth charts.

### How accurate is the percentile?

The maths follows the published WHO and CDC tables exactly. The measurement is the weak point: an error of 1 cm can move a percentile by several points. Measure without shoes, heels together, looking straight ahead.

### Does a tall child grow into a tall adult?

Often, but not always. Timing of puberty moves children up and down the chart in their early teens. For a rough adult height from the parents’ heights, see the height calculator.

## Sources

- Centers for Disease Control and Prevention, National Center for Health Statistics. CDC growth charts data files: stature-for-age, 2 to 20 years (statage.csv), with the LMS instructions. https://www.cdc.gov/growthcharts/cdc-data-files.htm
- Centers for Disease Control and Prevention. WHO growth charts data files: length-for-age, birth to 24 months (CDC copies of the WHO tables). https://www.cdc.gov/growthcharts/who-data-files.htm
- WHO Multicentre Growth Reference Study Group. WHO Child Growth Standards: length/height-for-age, weight-for-age, weight-for-length, weight-for-height and body mass index-for-age. Methods and development. Geneva: World Health Organization, 2006. https://www.who.int/publications/i/item/924154693X
- Kuczmarski RJ, Ogden CL, Guo SS, et al. 2000 CDC Growth Charts for the United States: methods and development. Vital Health Stat 11. 2002;(246):1-190. https://www.cdc.gov/nchs/data/series/sr_11/sr11_246.pdf
- Grummer-Strawn LM, Reinold C, Krebs NF. Use of World Health Organization and CDC growth charts for children aged 0-59 months in the United States. MMWR Recomm Rep. 2010;59(RR-9):1-15. https://www.cdc.gov/mmwr/preview/mmwrhtml/rr5909a1.htm