Mid-Parental Target Height Calculator

Mother height:

Measured adult height; changing the unit preserves the same physical height.

Father height:

Measured adult height; each parent may use a different input unit.

Child formula sex:

Choose the published girl or boy formula path; this is not a current height centile.

Headline method:

The selected method owns the summary; all three remain visible for comparison.

Family band:

Use the familiar clinic span or define a comparison half-width.

Custom half-width:

{{ formatNumber(custom_band_cm, 1) }} cm

Choose 4–15 cm; the midpoint remains unchanged.

Display precision:

Choose one or two decimal places without changing any target value.

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Review point	Current evidence	Use	Copy
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Population growth charts and family height answer different questions. A centile shows how a child compares with peers of the same age and sex. Mid-parental target height asks where adult height might sit given the measured adult heights of the child's biological parents.

The result is a family-context midpoint, not a prediction that a child will reach one exact number. Clinicians compare it with the child's measurements over time, growth velocity, pubertal timing, and projected adult height. A single current height cannot show whether growth is steady, slowing, or accelerating.

Measurements used in family target height interpretation
Measure	What it describes	What it cannot establish alone
Target midpoint	A central adult-height estimate derived from both biological parent heights.	The child's exact eventual height.
Family band	A comparison interval placed symmetrically around the selected midpoint.	A diagnosis or a guarantee that every healthy child falls inside it.
Height centile	The child's position within an age- and sex-specific reference population.	Whether growth is following the family's expected pattern.
Growth velocity	How much height changes over a measured period.	Adult height without age, puberty, history, and repeated measurements.

Measured parent heights are preferable to remembered values. A few centimetres of rounding can move the midpoint, while a large difference between the parents can make a simple add-or-subtract formula less representative. Regression-adjusted methods reduce the influence of unusually tall or short parental values by expressing each height as a z-score, which is its distance from an adult reference mean in standard-deviation units.

The sex path in these formulas is a mathematical reference choice tied to sex-specific adult height data. It does not describe gender identity, puberty stage, bone age, or an individual child's hormonal and medical context. The formula also assumes the entered adults are the biological parents whose heights supply the inherited family comparison.

Growth can differ from the family midpoint for many ordinary and medical reasons, including measurement error, nutrition, chronic illness, skeletal conditions, puberty timing, and population differences in the reference data. Concern is better assessed from a growth record and clinical history than from the midpoint or band alone.

How to Use This Tool:

Use measured adult heights and keep each value paired with its correct unit. The selected method changes the headline midpoint; it does not change the parent measurements.

Enter the biological mother's and father's adult heights. Centimetres and inches may be mixed because each parent has a separate unit selector.
Choose the girl's or boy's published formula path, then select Classic Tanner, UK Simple, or Regression-adjusted reference as the headline method.
Select the family band. Use the 8.5 cm or 10.2 cm preset only when that comparison convention fits your purpose; a custom half-width may be set from 4 to 15 cm.
Choose one or two decimal places for display, then compare the selected target with the other method values and the complete family band.
If no result appears, check that both heights resolve to 100 to 230 cm and that the unit and formula-sex choices are correct.

Interpreting Results:

Read Selected target as a family midpoint and Expected family band as the interval around it. A projected adult height near the edge is not automatically abnormal, and one outside the band is a reason to review the full growth pattern rather than draw a diagnosis.

Method comparison shows how much the midpoint changes under the three available formulas. A larger spread means the method choice matters more for this pair of parent heights. The regression-adjusted value is especially likely to differ when one or both parents are far from the adult reference mean.

Display precision changes only the printed value. Extra decimal places do not make parent measurements or the biological estimate more certain.

Technical Details:

The simple methods shift one parent's height to the child's sex-specific adult scale and then average the two values. The adjusted method instead converts both parents to z-scores, averages them, applies a 0.5 regression factor, and maps the result to the selected sex reference.

Formula Core:

The Classic Tanner midpoint uses a 13 cm offset. With mother height H_m and father height H_f, the two paths are:

\begin{matrix} T_{boy} & = & \frac{H_{m} + H_{f} + 13}{2} \\ T_{girl} & = & \frac{H_{m} + H_{f} - 13}{2} \end{matrix}

The UK Simple comparison uses the same equations with 12.5 cm in place of 13 cm. No intermediate value is rounded.

For the regression-adjusted comparison, the declared adult references are 162.9 cm with a 7.0 cm standard deviation for females and 176.2 cm with a 7.2 cm standard deviation for males.

z_{child} = \frac{\frac{H_{m} - 162.9}{7.0} + \frac{H_{f} - 176.2}{7.2}}{4}

T_{adjusted} = μ_{sex} + z_{child} σ_{sex}

Dividing the sum of parent z-scores by 4 is equivalent to averaging them and multiplying that average by 0.5. This pulls very high or low family estimates toward the adult reference mean.

Lookup and Band Core:

Target height methods and band widths
Choice	Exact rule	Interpretation
Classic Tanner	±13 cm sex offset before averaging	Published simple mid-parental method.
UK Simple	±12.5 cm sex offset before averaging	Close comparison with a slightly smaller offset.
Regression-adjusted	Parent z-score mean × 0.5, mapped to the sex reference	Reduces extremes and accounts for unequal parent positions in their reference distributions.
P5-P95 family band	Selected target ±8.5 cm	A symmetric comparison span used by the calculator.
AAP clinic span	Selected target ±10.2 cm	The four-inch range expressed in centimetres.
Custom band	Selected target ±4 to 15 cm	A user-defined comparison interval, not a new clinical standard.

The lower and upper limits are inclusive endpoints of the displayed interval. Heights are normalized to centimetres for calculation using 2.54 cm per inch. One- or two-decimal display rounding happens after all midpoint and band calculations.

Worked mechanism:

For a 165 cm mother, 180 cm father, and boy formula path, Classic Tanner gives 179.0 cm and UK Simple gives 178.75 cm. The parent z-scores are 0.300 and about 0.528; the adjusted child z-score is about 0.207, producing an adjusted target of about 177.69 cm. With the 8.5 cm band, that adjusted midpoint spans about 169.19 to 186.19 cm before display rounding.

Accuracy and Safety Notes:

Mid-parental target height is an informational family comparison, not a diagnosis or a substitute for pediatric assessment. The adjusted reference constants are fixed comparison values and may not represent every population.

Use repeated, accurately measured child heights and a suitable growth chart when assessing growth.
Seek clinical advice for slowed growth, a marked centile fall, symptoms of illness, puberty concerns, or a large mismatch between the child's growth pattern and family context.
Do not interpret a narrow custom band as added biological certainty.

References:

Mid-Parental Height, American Academy of Pediatrics EQIPP.
Information for Health Staff, Royal College of Paediatrics and Child Health Digital Growth Charts, updated 2026.
RCPCHGrowth library: Mid-Parental Height, Royal College of Paediatrics and Child Health Digital Growth Charts, updated 2026.