How to read a baby percentile chart
A percentile compares your baby with 100 babies of the same age and sex. The 40th percentile for weight means 40 of those babies weigh less. It is not a grade.
- Weight-for-age: the number most parents search for.
- Length-for-age: measured lying down until age 2.
- Head circumference: tracks brain growth in the first two years.
50th percentile weight and length by age (WHO)
| Age | Weight (boys · girls) | Length (boys · girls) |
|---|---|---|
| Birth | 7.4 lb (boys) · 7.1 lb (girls) | 19.7 in · 19.4 in |
| 3 months | 14.1 lb · 12.9 lb | 24.2 in · 23.6 in |
| 6 months | 17.5 lb · 16.1 lb | 26.6 in · 25.9 in |
| 9 months | 19.6 lb · 18.1 lb | 28.3 in · 27.6 in |
| 12 months | 21.3 lb · 19.6 lb | 29.8 in · 29.2 in |
| 18 months | 23.9 lb · 22.4 lb | 32.4 in · 31.8 in |
| 24 months | 26.5 lb · 25.0 lb | 34.2 in · 33.7 in |
Median values rounded from the WHO Child Growth Standards. Want your baby's exact percentile? Use the baby percentile calculator.
Motor milestones month by month
2 months
Holds head up briefly during tummy time; moves both arms and legs.
4 months
Holds head steady without support; pushes up on forearms; may roll tummy to back.
6 months
Rolls both ways; sits with support, leaning on hands.
9 months
Sits without support; gets into sitting; may crawl or scoot.
12 months
Pulls to stand; cruises along furniture; may take first steps.
15–18 months
Walks alone; climbs on and off furniture; starts to run stiffly.
24 months
Runs; kicks a ball; walks up a few stairs with help.
Based on CDC "Learn the Signs. Act Early." milestones (what most babies do by each age). For videos and delay signs, read motor milestones from birth to 5 or try the motor skills explorer.
When to call your pediatrician
- A measurement below the 3rd or above the 97th percentile.
- Crossing two major percentile lines between visits.
- No steady head control by 4 months, not sitting by 9 months, or not walking by 18 months.
- Losing a skill your baby already had.
Check your baby in 30 seconds
Enter age, weight, length and head size to get WHO percentiles with a plain-English explanation you can print for the checkup.
Open the growth calculatorCommon questions
What is a normal baby percentile?
Anything between the 3rd and 97th percentile is usually normal. A baby on the 10th percentile can be as healthy as one on the 90th; following their own curve matters most.
When should I worry about my baby's percentile?
Talk to your pediatrician if a measurement falls below the 3rd or above the 97th percentile, or if your baby crosses two major percentile lines (for example, from the 50th to below the 10th).
Does percentile predict motor milestones?
No. Bigger or smaller babies reach milestones on a similar timeline. Watch skills and growth separately.
Which chart should I use?
Pediatricians use WHO Growth Standards from birth to 2 years and CDC charts from 2 to 20 years. Our calculator switches automatically.
For general education only; it does not replace advice from your child's pediatrician.