Health tech
BabyPercentile
Free baby growth percentile calculator using WHO and CDC charts for children 0–5 years
BabyPercentile is a free, private calculator that compares a child's weight, length, and head circumference against WHO and CDC growth standards for ages 0–5
About BabyPercentile
BabyPercentile is a free tool that places children's measurements on WHO Child Growth Standards and CDC charts. It accepts weight, length or height, and head circumference for ages birth through 60 months, displaying results as percentiles and z-scores on interactive charts. The calculator handles special cases including premature babies with corrected age, boys versus girls with separate reference tables, and the switch from recumbent to standing measurement at 24 months. A private growth log saves measurements in the browser only, with no account or upload, and includes a trend alert based on UK NICE guidance for faltering growth. All calculation happens in JavaScript with no server-side processing or data collection beyond anonymous analytics.
What we found
- WHO Child Growth Standards charts for ages 0–60 months
- CDC 2000 growth charts available from age 24 months
- Weight, length/height, head circumference, and weight-for-length measurements
- Separate growth curves for boys and girls
- Corrected age calculation for premature babies born before 37 weeks
- Private browser-only growth log with no server upload
- Trend alert for faltering growth based on UK NICE guidance
- Gain-per-day check between measurements
- Works offline after initial page load
Pricing
Pricing model: Free
Common questions
- What does a percentile actually mean?
- If a baby is at the 40th percentile for weight, about 40% of babies of the same age and sex in the WHO reference population weigh less, and 60% weigh more. It is a position on a curve, not a score or a grade.
- Which growth standard does this calculator use?
- The calculator uses the WHO Child Growth Standards (2006), built from healthy, predominantly breastfed babies in six countries and covering birth to 60 months. From age 2 you can switch to the CDC 2000 charts.
- My baby was born early. Which age should I use?
- Tick 'Born before 37 weeks' and enter the weeks of pregnancy at birth. The calculator uses corrected age (calendar age minus the weeks born early) until 24 months, the convention most pediatricians follow.
- Where is the growth log stored and is it private?
- Saved measurements live only in your own browser's local storage on this device. Nothing is sent to the server or to anyone else, and the calculator works offline once the page has loaded.
- Is a low percentile something to worry about?
- Not by itself. Many healthy babies sit below the 15th percentile, and a single reading below the 3rd is often a small but healthy baby or a measuring slip. Re-measure it, and if it repeats, raise it with your pediatrician: a weight below the 2nd centile is one of the thresholds UK NICE guidance uses. What pediatricians watch most is the trend over time and whether weight keeps pace with length. A weight that keeps falling across percentiles is worth a check; see dropping percentiles for the thresholds clinicians use.
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