Parents are often handed a growth chart at check-ups and told their child is “on the 40th percentile for weight.” This calculator does the same job at home. Enter a child’s age, sex and weight, and it returns the percentile and z-score against the CDC 2000 weight-for-age charts, which cover children from 2 to 20 years, along with the weights at the 5th, 25th, 75th and 95th percentiles for that age so you can see the typical spread.
Weight-for-age has limits. It does not show whether a weight is healthy for the child’s height, which is why BMI-for-age is used to screen for under- and overweight in children.
How to use the child weight percentile calculator
- Select the child’s sex.
- Enter the age in years with a decimal for months.
- Enter the weight in kilograms or pounds.
- Read the percentile, z-score and the comparison weights.
Weight percentile formula (LMS method)
Percentile = Φ(z) × 100
Weight at a given z: M × (1 + L × S × z)1/L
L, M and S are the CDC parameters for each age in months and sex, interpolated between ages. Source: Kuczmarski RJ et al., 2000 CDC Growth Charts for the United States: Methods and development, Vital and Health Statistics Series 11, No. 246, 2002.
Worked example
A girl aged 8 years 1.5 months weighs 26.0 kg.
- The CDC median for girls at 97.5 months is M = 26.02 kg.
- Her weight is the median, so z = 0.00 and the percentile is the 50th.
- The 5th to 95th percentile range at this age is 20.3 to 36.7 kg (45 to 81 lb).
CDC weights by age: 5th, 50th and 95th percentiles
| Age (years) | Boys 5th | Boys 50th | Boys 95th | Girls 5th | Girls 50th | Girls 95th |
|---|---|---|---|---|---|---|
| 2 | 10.7 kg | 12.7 kg | 15.3 kg | 10.3 kg | 12.1 kg | 14.7 kg |
| 3 | 12.1 kg | 14.4 kg | 17.5 kg | 11.7 kg | 13.9 kg | 17.4 kg |
| 4 | 13.6 kg | 16.3 kg | 20.3 kg | 13.1 kg | 15.9 kg | 20.4 kg |
| 5 | 15.2 kg | 18.5 kg | 23.5 kg | 14.7 kg | 18.0 kg | 23.8 kg |
| 6 | 16.9 kg | 20.8 kg | 27.0 kg | 16.4 kg | 20.3 kg | 27.4 kg |
| 7 | 18.7 kg | 23.2 kg | 30.9 kg | 18.2 kg | 22.9 kg | 31.5 kg |
| 8 | 20.7 kg | 25.8 kg | 35.3 kg | 20.1 kg | 25.8 kg | 36.2 kg |
| 9 | 22.7 kg | 28.7 kg | 40.4 kg | 22.3 kg | 29.1 kg | 41.8 kg |
| 10 | 24.9 kg | 32.1 kg | 46.2 kg | 24.9 kg | 33.1 kg | 48.2 kg |
| 11 | 27.5 kg | 36.1 kg | 52.6 kg | 27.8 kg | 37.4 kg | 55.0 kg |
| 12 | 30.6 kg | 40.7 kg | 59.3 kg | 31.2 kg | 41.8 kg | 61.6 kg |
| 13 | 34.2 kg | 45.8 kg | 66.1 kg | 34.6 kg | 46.0 kg | 67.6 kg |
| 14 | 38.5 kg | 51.2 kg | 72.7 kg | 37.9 kg | 49.5 kg | 72.4 kg |
| 15 | 43.0 kg | 56.5 kg | 78.8 kg | 40.8 kg | 52.1 kg | 75.8 kg |
| 16 | 47.3 kg | 61.1 kg | 84.3 kg | 43.0 kg | 53.9 kg | 78.1 kg |
| 17 | 50.8 kg | 64.7 kg | 88.8 kg | 44.4 kg | 55.2 kg | 79.5 kg |
| 18 | 53.2 kg | 67.3 kg | 92.0 kg | 45.4 kg | 56.2 kg | 80.8 kg |
| 19 | 54.8 kg | 69.2 kg | 94.1 kg | 46.0 kg | 57.4 kg | 82.0 kg |
| 20 | 55.7 kg | 70.6 kg | 95.7 kg | 46.3 kg | 58.2 kg | 83.0 kg |
Using the result well
- Look at height too. A tall child is expected to weigh more; check the Child Height Percentile Calculator.
- BMI-for-age is the screening tool. The Child & Teen BMI Calculator combines height and weight and has CDC categories.
- Trends beat single readings. Compare with earlier measurements on the same scale.
- Do not put children on diets because of a percentile. Speak to a paediatrician, who will consider growth, eating, activity and family history.
This page is for information only and is not medical advice. A single measurement does not diagnose a problem; growth is judged over time. Talk to your child’s doctor about any concern.
Sources
- Kuczmarski RJ, Ogden CL, Guo SS, et al. 2000 CDC Growth Charts for the United States: Methods and development. Vital Health Stat 11(246), 2002.
- Centers for Disease Control and Prevention. Growth Chart Training: weight-for-age LMS parameters, 2–20 years.
Frequently asked questions
What does a weight percentile mean?
It compares a child’s weight with the CDC reference group of the same age and sex. A child at the 60th percentile weighs more than 60 out of 100 children of that age. It does not say whether a weight is healthy, because it ignores height.
Is weight-for-age enough to assess a child?
No. Weight should be read with height, and for children 2 and over the CDC recommends BMI-for-age to screen for underweight and overweight. Use the Child & Teen BMI Calculator for that.
What if my child is on a low or high percentile?
A child consistently on a low or high percentile who is growing along that line and is well is often healthy. Speak to a doctor if there is a sudden change, if weight is far from height percentile, or if you have concerns about eating or activity.
Which chart is used for children under 2?
The WHO standards, which the CDC recommends for ages 0 to 2. See the Baby Weight Percentile Calculator.
Do the charts include children with obesity?
The CDC 2000 weight-for-age chart is a reference built from national survey data collected between 1963 and 1994, with the weight data from the 1988–1994 survey excluded for children aged 6 and over to avoid the effect of rising obesity on the reference. It is a reference, not a recommendation of ideal weight.