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Baby growth percentile calculator
Check weight and length / height against WHO reference data for your baby’s age. Enter one measurement or both, then see what the percentile means.
YOUR REFERENCE POINT
See where your measurement sits
Add the measurement details, then choose Calculate. You can check weight, length / height, or both.
Keep the bigger picture
Sign in to record measurements over time in your child’s growth tracker.
Open the saved growth tracker →What does a growth percentile mean?
A percentile describes where a measurement sits in the reference for the same age and sex. Around the 50th percentile, roughly half of reference measurements are lower and half are higher. The 50th percentile is not a goal for every child.
One result cannot establish whether a baby is healthy or growing as expected. Accurate measurements over time, feeding, medical history and your clinician’s assessment provide context. Weight for age is not weight for length, BMI or a diagnosis.
How this calculator works
It calculates age in days on the measurement date and uses the WHO daily reference tables for boys or girls. The same reference calculations power BabyBloom’s saved growth tracker. This public tool supports ages 0–730 days, approximately 24 months.
At these ages, the length reference uses measurements taken lying down. If you enter standing height, 0.7 cm is added for comparison using the WHO conversion. The recorded value is shown alongside the converted value. Kilograms and centimetres are used for the calculation; pound and inch entries are converted first.
This simplified calculator uses age since birth. For babies born before 37 weeks, or if birth timing is unknown, it does not produce a percentile. Ask your clinician about corrected age and an appropriate growth chart.
References can differ by country and age. In U.S. clinical practice, CDC recommends WHO charts before age 2 and CDC charts from age 2. Compare follow-up measurements using the chart your healthcare team recommends.
Common questions
Can I check height without entering weight?
Yes. Enter length / height and the measurement position. Weight is optional. You can also calculate weight alone.
Why is a length percentile sometimes unavailable?
The calculator needs an age, chart reference, positive measurement and the position used to measure. It also checks its supported age range and birth timing. An unavailable result does not establish a growth problem.
What if the result is very high or very low?
Check the date, units, measurement and chart reference. Percentiles near the ends of the displayed range are shown as below 0.1st or above 99.9th rather than as an exact tail estimate. Discuss concerns or changes over time with your clinician.
Will this save the measurement?
No. This calculator does not save or transfer entries. To build a history, sign in to your growth tracker and record measurements there.
Sources and review status
BabyBloom built this calculator using published WHO reference data. No clinical review or WHO endorsement of this tool is claimed. Read our editorial standards or report a correction.
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