Baby Percentile Calculator (WHO, 0-24 Months)
For babies 0-24 months: enter sex, age, and length, weight, and head circumference to get all four WHO percentiles -- length-for-age, weight-for-age, head-circumference-for-age, and weight-for-length -- in one form.
Length-for-age
18th percentile
z-score -0.91
Weight-for-age
21st percentile
z-score -0.79
Head circumference-for-age
17th percentile
z-score -0.95
Weight-for-length
41st percentile
z-score -0.23
Corrected age, worked example
A baby born at 32 weeks gestation, now 4 months (17.4 weeks) old chronologically: born 8 weeks early (40 − 32), which is 8 / 4.345 ≈ 1.84 months. Corrected age = 4 − 1.84 ≈ 2.2 months -- that's the age used to look up percentiles, not the 4 months since birth.
If you're also tracking naps and night sleep at this age, SleepSums' nap calculator works from the same age-in-months input.
Frequently Asked Questions
What is weight-for-length, and why is it here alongside weight-for-age?
Weight-for-age compares your baby's weight to other babies the same age. Weight-for-length compares weight to other babies the same length, regardless of age -- which is often the more useful number, because it separates 'small for their age' from 'thin for their size.' A baby can be a low weight-for-age percentile just because they're short, while landing at a completely normal weight-for-length.
How does corrected age work, and when should I use it?
For a baby born before 37 weeks, subtract the number of weeks born early from their age in weeks, then convert to months -- that's roughly what the checkbox above does automatically. Most pediatricians use corrected age for growth percentiles until about 24 months, after which the difference stops mattering much.
Should all four numbers be at the same percentile?
No -- there's no rule that they should match, and most babies' four percentiles aren't identical. What matters more is that each one stays roughly on its own curve over time, not that length, weight, and head circumference agree with each other on any single visit.
My baby is past 24 months -- what do I use instead?
Past 24 months, height and weight percentiles continue on the height percentile calculator and weight percentile calculator, which switch to the CDC 2000 charts automatically.
These calculators estimate from published population reference data (the CDC and WHO growth charts) and published rules of thumb -- not a diagnosis, and not a substitute for your pediatrician, who tracks your child's own growth curve over time and knows their history.