Baby percentile calculator
Enter your child's sex, date of birth and measurements to see where they sit on the World Health Organization growth charts for weight, length or height, and head circumference, from birth to 5 years.
Results
How to use it
- Choose boy or girl and enter the date of birth. The measurement date is today unless you change it.
- Enter any of the measurements you have: weight, length or height, and head circumference. You can switch between kg and cm or lb and inches.
- Read the percentile, the z-score and the WHO median for that age; the tables below show the 3rd, 50th and 97th percentiles month by month.
What a percentile means
A percentile compares one measurement with children of the same age and sex on the WHO charts. If a baby's weight is on the 25th percentile, about 25 in 100 babies of the same age and sex weigh less and about 75 weigh more. The 50th percentile is the median.
There is no best percentile. A small, healthy baby can stay on a low line and a big one on a high line. What matters most is how your child grows over time: the NHS notes that measurements often move up or down by one line, but crossing two lines is less common and worth talking to your health visitor about.
When to ask a doctor
With the WHO charts, the US Centers for Disease Control and Prevention (CDC) recommends cut-offs 2 standard deviations below and above the median, the 2.3rd and 97.7th percentiles (labelled the 2nd and 98th on its charts). A measurement beyond them is a reason for a professional to take a closer look, not a diagnosis.
One reading from home scales or a tape measure can be off. If a result surprises you, if your child seems unwell, or if growth has slowed down or sped up sharply, talk to your doctor or health visitor.
WHO percentile tables, birth to 5 years
Weight-for-age (kg)
| Age | Boys | Girls | ||||
|---|---|---|---|---|---|---|
| 3rd | 50th | 97th | 3rd | 50th | 97th | |
| Birth | 2.5 | 3.3 | 4.3 | 2.4 | 3.2 | 4.2 |
| 1 month | 3.4 | 4.5 | 5.7 | 3.2 | 4.2 | 5.4 |
| 2 months | 4.4 | 5.6 | 7.0 | 4.0 | 5.1 | 6.5 |
| 3 months | 5.1 | 6.4 | 7.9 | 4.6 | 5.8 | 7.4 |
| 4 months | 5.6 | 7.0 | 8.6 | 5.1 | 6.4 | 8.1 |
| 5 months | 6.1 | 7.5 | 9.2 | 5.5 | 6.9 | 8.7 |
| 6 months | 6.4 | 7.9 | 9.7 | 5.8 | 7.3 | 9.2 |
| 7 months | 6.7 | 8.3 | 10.2 | 6.1 | 7.6 | 9.6 |
| 8 months | 7.0 | 8.6 | 10.5 | 6.3 | 7.9 | 10.0 |
| 9 months | 7.2 | 8.9 | 10.9 | 6.6 | 8.2 | 10.4 |
| 10 months | 7.5 | 9.2 | 11.2 | 6.8 | 8.5 | 10.7 |
| 11 months | 7.7 | 9.4 | 11.5 | 7.0 | 8.7 | 11.0 |
| 12 months | 7.8 | 9.6 | 11.8 | 7.1 | 8.9 | 11.3 |
| 13 months | 8.0 | 9.9 | 12.1 | 7.3 | 9.2 | 11.6 |
| 14 months | 8.2 | 10.1 | 12.4 | 7.5 | 9.4 | 11.9 |
| 15 months | 8.4 | 10.3 | 12.7 | 7.7 | 9.6 | 12.2 |
| 16 months | 8.5 | 10.5 | 12.9 | 7.8 | 9.8 | 12.5 |
| 17 months | 8.7 | 10.7 | 13.2 | 8.0 | 10.0 | 12.7 |
| 18 months | 8.9 | 10.9 | 13.5 | 8.2 | 10.2 | 13.0 |
| 19 months | 9.0 | 11.1 | 13.7 | 8.3 | 10.4 | 13.3 |
| 20 months | 9.2 | 11.3 | 14.0 | 8.5 | 10.6 | 13.5 |
| 21 months | 9.3 | 11.5 | 14.3 | 8.7 | 10.9 | 13.8 |
| 22 months | 9.5 | 11.8 | 14.5 | 8.8 | 11.1 | 14.1 |
| 23 months | 9.7 | 12.0 | 14.8 | 9.0 | 11.3 | 14.3 |
| 24 months | 9.8 | 12.2 | 15.1 | 9.2 | 11.5 | 14.6 |
| 30 months | 10.7 | 13.3 | 16.6 | 10.1 | 12.7 | 16.2 |
| 36 months | 11.4 | 14.3 | 18.0 | 11.0 | 13.9 | 17.8 |
| 42 months | 12.2 | 15.3 | 19.4 | 11.8 | 15.0 | 19.5 |
| 48 months | 12.9 | 16.3 | 20.9 | 12.5 | 16.1 | 21.1 |
| 54 months | 13.6 | 17.3 | 22.3 | 13.2 | 17.2 | 22.8 |
| 60 months | 14.3 | 18.3 | 23.8 | 14.0 | 18.2 | 24.4 |
Length/height-for-age (cm)
| Age | Boys | Girls | ||||
|---|---|---|---|---|---|---|
| 3rd | 50th | 97th | 3rd | 50th | 97th | |
| Birth | 46.3 | 49.9 | 53.4 | 45.6 | 49.1 | 52.7 |
| 1 month | 51.1 | 54.7 | 58.4 | 50.0 | 53.7 | 57.4 |
| 2 months | 54.7 | 58.4 | 62.2 | 53.2 | 57.1 | 60.9 |
| 3 months | 57.6 | 61.4 | 65.3 | 55.8 | 59.8 | 63.8 |
| 4 months | 60.0 | 63.9 | 67.8 | 58.0 | 62.1 | 66.2 |
| 5 months | 61.9 | 65.9 | 69.9 | 59.9 | 64.0 | 68.2 |
| 6 months | 63.6 | 67.6 | 71.6 | 61.5 | 65.7 | 70.0 |
| 7 months | 65.1 | 69.2 | 73.2 | 62.9 | 67.3 | 71.6 |
| 8 months | 66.5 | 70.6 | 74.7 | 64.3 | 68.7 | 73.2 |
| 9 months | 67.7 | 72.0 | 76.2 | 65.6 | 70.1 | 74.7 |
| 10 months | 69.0 | 73.3 | 77.6 | 66.8 | 71.5 | 76.1 |
| 11 months | 70.2 | 74.5 | 78.9 | 68.0 | 72.8 | 77.5 |
| 12 months | 71.3 | 75.7 | 80.2 | 69.2 | 74.0 | 78.9 |
| 13 months | 72.4 | 76.9 | 81.5 | 70.3 | 75.2 | 80.2 |
| 14 months | 73.4 | 78.0 | 82.7 | 71.3 | 76.4 | 81.4 |
| 15 months | 74.4 | 79.1 | 83.9 | 72.4 | 77.5 | 82.7 |
| 16 months | 75.4 | 80.2 | 85.1 | 73.3 | 78.6 | 83.9 |
| 17 months | 76.3 | 81.2 | 86.2 | 74.3 | 79.7 | 85.0 |
| 18 months | 77.2 | 82.3 | 87.3 | 75.2 | 80.7 | 86.2 |
| 19 months | 78.1 | 83.2 | 88.4 | 76.2 | 81.7 | 87.3 |
| 20 months | 78.9 | 84.2 | 89.5 | 77.0 | 82.7 | 88.4 |
| 21 months | 79.7 | 85.1 | 90.5 | 77.9 | 83.7 | 89.4 |
| 22 months | 80.5 | 86.0 | 91.6 | 78.7 | 84.6 | 90.5 |
| 23 months | 81.3 | 86.9 | 92.6 | 79.6 | 85.5 | 91.5 |
| 24 months | 81.4 | 87.1 | 92.9 | 79.6 | 85.7 | 91.8 |
| 30 months | 85.5 | 91.9 | 98.3 | 84.0 | 90.7 | 97.3 |
| 36 months | 89.1 | 96.1 | 103.1 | 87.9 | 95.1 | 102.2 |
| 42 months | 92.4 | 99.9 | 107.3 | 91.4 | 99.0 | 106.7 |
| 48 months | 95.4 | 103.3 | 111.2 | 94.6 | 102.7 | 110.8 |
| 54 months | 98.4 | 106.7 | 115.0 | 97.6 | 106.2 | 114.7 |
| 60 months | 101.2 | 110.0 | 118.7 | 100.5 | 109.4 | 118.4 |
Head circumference-for-age (cm)
| Age | Boys | Girls | ||||
|---|---|---|---|---|---|---|
| 3rd | 50th | 97th | 3rd | 50th | 97th | |
| Birth | 32.1 | 34.5 | 36.9 | 31.7 | 33.9 | 36.1 |
| 1 month | 35.1 | 37.3 | 39.5 | 34.3 | 36.5 | 38.8 |
| 2 months | 36.9 | 39.1 | 41.3 | 36.0 | 38.3 | 40.5 |
| 3 months | 38.3 | 40.5 | 42.7 | 37.2 | 39.5 | 41.9 |
| 4 months | 39.4 | 41.6 | 43.9 | 38.2 | 40.6 | 43.0 |
| 5 months | 40.3 | 42.6 | 44.8 | 39.0 | 41.5 | 43.9 |
| 6 months | 41.0 | 43.3 | 45.6 | 39.7 | 42.2 | 44.6 |
| 7 months | 41.7 | 44.0 | 46.3 | 40.4 | 42.8 | 45.3 |
| 8 months | 42.2 | 44.5 | 46.9 | 40.9 | 43.4 | 45.9 |
| 9 months | 42.6 | 45.0 | 47.4 | 41.3 | 43.8 | 46.3 |
| 10 months | 43.0 | 45.4 | 47.8 | 41.7 | 44.2 | 46.8 |
| 11 months | 43.4 | 45.8 | 48.2 | 42.0 | 44.6 | 47.1 |
| 12 months | 43.6 | 46.1 | 48.5 | 42.3 | 44.9 | 47.5 |
| 13 months | 43.9 | 46.3 | 48.8 | 42.6 | 45.2 | 47.7 |
| 14 months | 44.1 | 46.6 | 49.0 | 42.9 | 45.4 | 48.0 |
| 15 months | 44.3 | 46.8 | 49.3 | 43.1 | 45.7 | 48.2 |
| 16 months | 44.5 | 47.0 | 49.5 | 43.3 | 45.9 | 48.5 |
| 17 months | 44.7 | 47.2 | 49.7 | 43.5 | 46.1 | 48.7 |
| 18 months | 44.9 | 47.4 | 49.9 | 43.6 | 46.2 | 48.8 |
| 19 months | 45.0 | 47.5 | 50.0 | 43.8 | 46.4 | 49.0 |
| 20 months | 45.2 | 47.7 | 50.2 | 44.0 | 46.6 | 49.2 |
| 21 months | 45.3 | 47.8 | 50.4 | 44.1 | 46.7 | 49.4 |
| 22 months | 45.4 | 48.0 | 50.5 | 44.3 | 46.9 | 49.5 |
| 23 months | 45.6 | 48.1 | 50.7 | 44.4 | 47.0 | 49.7 |
| 24 months | 45.7 | 48.3 | 50.8 | 44.6 | 47.2 | 49.8 |
| 30 months | 46.3 | 48.9 | 51.6 | 45.3 | 47.9 | 50.6 |
| 36 months | 46.8 | 49.5 | 52.1 | 45.9 | 48.5 | 51.2 |
| 42 months | 47.2 | 49.9 | 52.6 | 46.3 | 49.0 | 51.6 |
| 48 months | 47.5 | 50.2 | 53.0 | 46.7 | 49.3 | 52.0 |
| 54 months | 47.7 | 50.5 | 53.3 | 47.0 | 49.6 | 52.3 |
| 60 months | 47.9 | 50.7 | 53.5 | 47.2 | 49.9 | 52.6 |
Lengths up to 24 months are measured lying down; heights from 24 months standing up.
Weight and length by age
- Newborn
- 1 month
- 2 months
- 3 months
- 4 months
- 5 months
- 6 months
- 7 months
- 8 months
- 9 months
- 10 months
- 11 months
- 12 months
- 13 months
- 14 months
- 15 months
- 16 months
- 17 months
- 18 months
- 19 months
- 20 months
- 21 months
- 22 months
- 23 months
- 24 months
- 3 years
- 4 years
- 5 years
Why this calculator uses the WHO charts
The WHO Child Growth Standards show how healthy children grow in good conditions from birth to 5 years, based on children from six countries. The CDC recommends them for all children under 2 in the United States, and the UK's growth charts for this age are also based on them. Length is measured lying down until 2 years and height standing up after that, so the WHO height curve starts about 0.7 cm below the length curve at 2 years.
Frequently asked questions
What percentile should my baby be?
There is no ideal percentile. Most children sit between the 2nd and 98th percentile lines, and a child who follows their own line steadily is usually growing well. A sudden drop or rise across lines is worth discussing with your doctor or health visitor.
Is the 50th percentile average?
It is the median: half of the children of the same age and sex on the WHO charts measure less and half measure more. Being above or below it is not good or bad in itself.
How much should a 6-month-old baby weigh?
On the WHO charts the median weight at 6 months is 7.9 kg (17.5 lb) for boys and 7.3 kg (16.1 lb) for girls. Between the 3rd and 97th percentiles are 6.4–9.7 kg (14.2–21.4 lb) for boys and 5.8–9.2 kg (12.8–20.3 lb) for girls.
How long should a 1-year-old be?
On the WHO charts the median length at 12 months is 75.7 cm (29.8 in) for boys and 74.0 cm (29.1 in) for girls. Between the 3rd and 97th percentiles are 71.3–80.2 cm (28.1–31.6 in) for boys and 69.2–78.9 cm (27.2–31.0 in) for girls.
My baby dropped a percentile line. Should I worry?
Moving by one line is common, especially in the first weeks. The NHS says crossing two lines is less common; if that happens, or if your baby seems unwell or is feeding poorly, talk to your health visitor or doctor.
Why use the WHO growth charts?
The CDC itself recommends the WHO growth standards for children under 2 in the United States. They show how children grow in healthy conditions, while older reference charts describe how one population happened to grow at one time.
Sources
- WHO: Child growth standards (weight-for-age, length/height-for-age, head circumference-for-age)
- 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)
- NHS: Your baby's weight and height
Also try: Child height calculator