Newborn & Infant Growth Percentile Calculator
Free WHO-standard growth percentile calculator for weight, length/height & head circumference — ages 0 to 36 months. Instant percentile, z-score, and growth curve chart.
Calculate Your Baby’s Growth Percentile
Results
Growth Curve
Medically reviewed by Dr. Ruqaiya Khan, MD, FACOG
Board-certified OB-GYN. This calculator and its accompanying content were reviewed for clinical accuracy against WHO Child Growth Standards on June 2026. View reviewer credentials →
How Newborn Growth Percentiles Work
A growth percentile compares your baby’s weight, length, and head circumference to a reference population of healthy children of the same age and sex. If your baby is in the 60th percentile for weight, that means roughly 60% of babies of the same age and sex weigh the same or less — not that your baby weighs “60% of normal.” Percentiles describe position within a healthy range, not a grade or score.
Why We Use WHO Growth Standards (Not CDC)
This calculator is built on the World Health Organization (WHO) Child Growth Standards, the global benchmark recommended for children from birth to 24 months (extended here to 36 months). Unlike older reference charts built from formula-fed infants in a single country, the WHO standards were developed from a multi-country study of healthy, predominantly breastfed children raised in optimal conditions — describing how children should grow rather than simply how a sample population happened to grow. The American Academy of Pediatrics (AAP) and CDC both recommend WHO standards for children under 2.
Understanding Your Results
| Percentile Range | What It Means |
|---|---|
| 3rd–10th | Lower end of typical range; pediatrician may monitor trend |
| 10th–90th | Typical, healthy range |
| 90th–97th | Higher end of typical range |
| Below 3rd or above 97th | Outside typical range — discuss with your pediatrician |
A single measurement matters less than the trend over time. A baby steadily tracking along the 25th percentile is generally healthier than one who drops from the 60th to the 15th percentile in a few months, even though the second number is still “typical.” Pediatricians watch for percentile crossing (a sudden jump across two or more major percentile lines) as the real signal worth investigating.
Weight, Length, and Head Circumference — What Each One Tells You
Weight is the most variable measurement and the most sensitive to short-term factors like feeding, illness, or a recent growth spurt. Length reflects longer-term growth and is more stable. Head circumference tracks brain growth and is closely monitored in the first year for both undergrowth (microcephaly) and overgrowth (macrocephaly) concerns.
When to Contact Your Pediatrician
- Weight percentile drops by two or more major lines between checkups
- Measurement falls below the 3rd or above the 97th percentile
- Weight-for-length is significantly out of proportion
- Your baby was born premature (ask about corrected age adjustments)
- Any other feeding, development, or behavior concerns
Related Reading
- Pregnancy Week by Week — a full timeline of pregnancy
- First Trimester Guide — weeks 1 to 13
- Second Trimester Guide — weeks 14 to 27
- Third Trimester Guide — weeks 28 to birth
Also see our calculator FAQs, pregnancy FAQs and pregnancy terms glossary.
Frequently Asked Questions
Using the Newborn Percentile Calculator
Our newborn percentile calculator uses WHO growth standards to compare your baby’s weight, length, and head circumference to other infants of the same age. Once you know where your newborn falls, our Pregnancy BMI Calculator can help you track your own postpartum health, and the CDC growth charts page offers further detail on how these percentiles are calculated.