Work out growth chart percentile instantly with clear inputs, formula shown and shareable results.
Any charted measurement becomes a z-score of (value - mean) / standard deviation, and the normal curve maps that to a centile which is then matched to the nearest printed chart line. Paper charts only print a handful of centile lines, so knowing both the exact centile and the nearest line makes plotting and reporting consistent.
SD score
z = (measured value - reference mean) / reference standard deviation
Centile
centile = normal cumulative distribution of z x 100
z = (measured value - reference mean) / reference standard deviation. Any charted measurement becomes a z-score of (value - mean) / standard deviation, and the normal curve maps that to a centile which is then matched to the nearest printed chart line.
Paper charts only print a handful of centile lines, so knowing both the exact centile and the nearest line makes plotting and reporting consistent.
Enter measurement type, measured value, reference mean for age and sex, reference standard deviation. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.