Baby Percentile Calculator
Track your baby's growth against WHO growth charts. See weight, length, and head circumference percentiles.
Enter Your Values
Enter your values and press Calculate: you will get the result, its method, the inputs used and confidence, plus copy, print and share options.
How this calculator works
WHO growth standard percentilesv1.0.0
LMS-based z-scores for weight-, length- and head-circumference-for-age (0-24 months).
- Applies to
- Infants and toddlers 0-24 months (breastfed reference population)
- Assumptions
- Term, healthy growth context
- Limitations
- A single percentile is not a growth assessment; trends matter
- Output
- percentile / z-score
- Last reviewed
- 2026-06-01
Evidence Sources & Literature
- World Health Organization. WHO Child Growth Standards: length/height-for-age, weight-for-age, head circumference-for-age (LMS). WHO Multicentre Growth Reference Study, 2006. <a href="https://www.who.int/tools/child-growth-standards" rel="nofollow noopener" target="_blank">Source</a>.
About the Baby Percentile Calculator
This calculator shows where your baby's weight, length or head circumference falls compared with other babies of the same age and sex, expressed as a percentile. Percentiles are the same tool pediatricians use at check-ups, and understanding them can turn a confusing number into reassurance. If your baby is in the 40th percentile for weight, it simply means they weigh more than about 40 percent of babies their age.
As a parent myself in spirit on this page, I want to lead with the most important message: there is no good or bad percentile. Healthy babies come in a wide range of sizes, and what matters far more than the number is steady, consistent growth along their own curve. Your pediatrician is always the best guide.
What a percentile actually means
A percentile ranks your baby against a large reference group of babies the same age and sex. The 50th percentile is simply the middle, not a target. Being in the 15th or the 85th percentile is perfectly healthy for many babies; it just describes where they sit in the normal range. Percentiles are descriptive, not a grade, and the full healthy range is genuinely wide.
Why the trend matters more than the number
This is the point pediatricians stress most. A baby who consistently tracks along the 20th percentile is usually growing beautifully, because they are following their own steady curve. What draws attention is not a particular percentile but a sudden change, such as dropping or jumping across several percentile lines, which is worth a conversation. One snapshot tells you far less than the pattern over time.
Which charts are used
For babies, growth is usually plotted on standardized charts (the World Health Organization charts are recommended for infants in many countries, especially for breastfed babies). The calculator uses standard reference data for weight, length and head circumference by age and sex. Head circumference is included because it reflects healthy brain growth in the early months, which is why your pediatrician measures it.
When to talk to your pediatrician
Use this calculator for understanding and gentle reassurance, and let your pediatrician do the real interpretation. They plot growth over time, factor in your baby's history and feeding, and know what is normal for your child. If you are worried about feeding, growth or a big change in percentile, that is always a good reason to reach out. Trust the trend, trust your instincts, and trust your child's doctor.
Dietitian Insight: WHO growth curves assess infant mass and length percentiles across pediatric developmental stages. Discover clinical recommendations on pediatric growth and development guidance, or project adult stature using our mid-parental height predictor.
Sources & method
This calculator uses established, peer-reviewed formulas and reference ranges from recognized health and nutrition authorities. Results are estimates for general education, not a medical diagnosis. For decisions about your health, consult a qualified clinician. Reviewed by Macro & Meals Editorial Team, Content editor.
Frequently Asked Questions
What does my baby's percentile mean?
A percentile shows where your baby's weight, length or head circumference falls compared with other babies of the same age and sex. The 50th percentile is simply the middle, not a target. Being in the 15th or 85th percentile is perfectly healthy; it just describes where your baby sits in the normal range.
Is a low or high percentile bad?
No. Healthy babies come in a wide range of sizes, so there is no good or bad percentile. What matters is steady growth along your baby's own curve. A consistent low or high percentile is usually fine; a sudden jump or drop across several lines is what warrants a conversation with your pediatrician.
Why does steady growth matter more than the number?
Because a baby following their own curve, even a lower one, is typically growing well. Pediatricians watch the trend over time rather than a single snapshot. A sudden change across percentile lines is more meaningful than the particular percentile itself.
Which growth charts does this use?
It uses standard reference data for weight, length and head circumference by age and sex. For infants, the World Health Organization charts are recommended in many countries, especially for breastfed babies. Your pediatrician will plot growth on the appropriate chart over time.
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