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Growth Chart Percentile Calculator

Work out growth chart percentile instantly with clear inputs, formula shown and shareable results.

About Growth Chart Percentile Calculator

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.

Formulas

SD score

z = (measured value - reference mean) / reference standard deviation

Centile

centile = normal cumulative distribution of z x 100

Worked example

With the default values below, Growth Chart Percentile Calculator returns Percentile of 65.5%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Measurement typeone of Height / length, Weight, Head circumference, BMI
Height / length
Measured valueminimum 0.1
120
Reference mean for age and sexminimum 0.1
118
Reference standard deviationminimum 0.01
5

Results

Percentile
65.5%
Z-score (SD score)
0.400
Nearest printed centile line
75
How to read it
height sits on roughly the 75th centile line

Step by step

  1. 1Values used
  2. 2SD score
  3. 3Centile
  4. 4Percentile= 65.5
  5. 5Z-score (SD score)= 0.400
  6. 6Nearest printed centile line= 75
  7. 7How to read it= height sits on roughly the 75th centile line

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the Growth Chart Percentile figure worked out?

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.

Why does this matter?

Paper charts only print a handful of centile lines, so knowing both the exact centile and the nearest line makes plotting and reporting consistent.

What do I need to enter?

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.

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