Baby Growth Percentile Calculator
Estimate your baby's weight percentile compared to WHO growth references.
Assumptions used in this calculation
- Simplified reference: Interpolates between a reduced set of WHO checkpoints (0, 3, 6, 9, 12, 18, 24 months) rather than using the full LMS growth curve.WHO Child Growth Standards
About this calculator
A baby's weight on its own doesn't say much, what matters to parents and pediatricians is how that weight compares to other babies the same age, which requires plotting it against a WHO growth reference curve and reading off a percentile, math that isn't practical to do by hand. This calculator estimates that weight-for-age percentile directly: enter your baby's age in months and current weight, and it calculates a z-score (how far the weight sits from the reference median in standard deviations) using a simplified, interpolated set of WHO growth reference points from 0-24 months, separately for boys and girls, then converts that z-score into a percentile via the normal distribution. A result near the 50th percentile means average for that age and sex; higher or lower percentiles show where your baby falls relative to the reference population. Because this uses interpolated checkpoints rather than the full WHO growth curve, it's a general estimate, use your pediatrician's official growth chart for an accurate clinical read.
Worked example
Boy, 12 months, 9.6 kg
Result: ≈ 50th percentile (at the reference median)
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