Dr. BabyFree growth tool · Birth to 24 months
Baby weight
percentile calculator.
Baby weight percentile calculator. Compare a measurement with the WHO reference for babies of the same age and sex.
Every baby has
their own curve.
Enter a measurement to see the percentile and reference chart.
Measurements you’ve saved
Only saved when you choose. Stored in this browser, not sent to Dr. Baby.
What does an infant weight percentile mean?
A percentile compares your baby’s weight with the WHO reference population at the same age and sex. The 50th percentile is the median, not a target. A single measurement does not diagnose a health condition.
How this calculator works
We calculate age from the birth and measurement dates, then use the WHO daily L, M and S weight-for-age parameters and a normal-distribution conversion. Pounds are converted to kilograms. Results outside ±3 z-scores are shown as an approximate range rather than a precise percentile.
The tool supports birth to the second birthday. It does not adjust for prematurity or assess weight relative to length. Your pediatrician interprets growth alongside your baby’s history.
Explore percentiles, one dot at a time →A useful place to start
How to use this tool
- Choose the WHO girls or boys reference, then enter birth and measurement dates.
- Enter weight in kilograms or pounds. The calculator converts pounds before using the daily WHO reference.
- Read the percentile and chart together. Save the result on this device only if you want a local record.
Baby growth chart: weight for age
This infant weight percentile calculator includes a weight-for-age reference chart. It is one type of baby growth chart: it does not cover length or head circumference. Save repeated measurements to keep a local weight history, and interpret the pattern with your pediatrician.
Questions about baby weight percentile calculator
Can I calculate an infant weight percentile in pounds?
Yes. Select Pounds (lb). The calculator converts your entry to kilograms using 1 lb = 0.45359237 kg before calculating the percentile.
Is this a baby BMI or length percentile calculator?
No. This tool calculates weight for age only. It does not calculate BMI, length for age or weight for length. A weight-for-age result cannot replace those measurements.
Does the calculator use adjusted age for premature babies?
No. It uses the actual number of days between birth and measurement. The adjusted age calculator explains a separate age calculation; your clinician should choose the growth reference and age appropriate for your baby.
Why can another growth calculator show a different result?
Check that both use the same reference, sex, date, measurement and units. This tool uses daily WHO LMS data; rounded ages or a different reference can change the result.
Content updated · Methods, sources & limitations