Baby weight percentile calculator
Find your baby’s weight percentile, plus length and head circumference percentiles, on the WHO Child Growth Standards (birth to 5 years) or the CDC infant charts (birth to 36 months). It takes a few seconds and needs no account.
Enter a date of birth and at least one measurement to see the percentile.
Also: growth chart calculator for girls · for boys · newborn weight chart by week · em português
What the result means
A percentile compares one measurement with children of the same age and sex. If your daughter’s weight is at the 40th percentile, she weighs more than about 40 out of 100 girls her age and less than about 60.
The z-score says the same thing in standard deviations from the median: 0 is the median, −1 and +1 are roughly the 16th and 84th percentiles, and −2 and +2 are roughly the 2nd and 98th.
In the UK and Ireland percentiles are called centiles. The UK-WHO charts in the Red Book and the HSE charts draw lines at the 0.4th, 2nd, 9th, 25th, 50th, 75th, 91st, 98th and 99.6th centiles; this calculator gives the exact centile between those lines.
Neither number is a grade. Healthy children grow along every part of the chart, and pediatricians mostly watch whether a child keeps to a similar curve from one checkup to the next.
WHO growth charts by month
Common questions
How is the percentile calculated?
Growthling uses the LMS method published with the WHO and CDC growth charts. For your child’s exact age it looks up three values (L, M and S), turns the measurement into a z-score with Z = ((X / M)^L − 1) / (L × S), and converts the z-score into a percentile.
What percentile is normal for a baby?
Anything between the 3rd and the 97th percentile is within the usual range on these charts. What matters most is that a child keeps following roughly the same curve over time.
Should I use the WHO or the CDC chart?
The CDC recommends the WHO growth charts for children under 2 years in the United States, and the CDC charts from age 2. This calculator covers WHO from birth to 5 years and the CDC infant charts from birth to 36 months.
Does it work as a centile calculator for the UK and Ireland?
Yes. A centile is the same thing as a percentile. The UK-WHO charts in the Red Book, also used by the HSE in Ireland since 2013, are the WHO standards from 2 weeks to 4 years, which is what this calculator uses on the WHO setting. Those charts draw nine centile lines: 0.4th, 2nd, 9th, 25th, 50th, 75th, 91st, 98th and 99.6th. The calculator gives the exact centile, so a result of 30 sits between the 25th and 50th lines. At birth, UK-WHO charts use British birth data, so results in the first two weeks can differ slightly.
Can I use it for a premature baby?
The calculator uses actual age. For babies born early, pediatricians often use corrected age for the first two years, so ask yours which age to use.
Is anything I type saved?
No. The calculator runs in your browser and the numbers you enter are not sent to us. Sign up if you want to save measurements and see them on a growth chart.
Sources: WHO Child Growth Standards and CDC growth charts. For information only; not medical advice.