Foetal Growth Percentile Calculator

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

About Foetal Growth Percentile Calculator

Converts an estimated foetal weight into a percentile against the gestation-specific reference mean and standard deviation you supply.

Formula

Percentile from z-score

z = (estimated weight - reference mean) / reference SD; percentile = 100 x Phi(z)

Worked example

With the default values below, Foetal Growth Percentile Calculator returns Growth percentile of 19.6%. Change any input above and every figure here is recalculated in your browser.

Inputs used

Estimated foetal weightaccepts 200–6,000 g: 2,600 g
Reference mean weight for gestationaccepts 200–6,000 g: 2,900 g
Reference standard deviationaccepts 20–900 g: 350 g

Results

Growth percentile: 19.6%
Z-score: -0.86
Classification: Within the 10th to 90th centile range

Step by step

1Values used
2Percentile from z-score
3Growth percentile= 19.6
4Z-score= -0.86
5Classification= Within the 10th to 90th centile range

Assumptions and limits

The result is derived only from the 3 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 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

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

Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

Frequently Asked Questions

Which reference chart should be used?

Customised or INTERGROWTH-21st charts are common; the reference values entered should match the chart in use.

Is small for gestational age the same as growth restriction?

No. Growth restriction implies a pathological failure to reach growth potential, which some constitutionally small babies do not have.