Mid-Parental Target Height Calculator

Height unit:

Choose cm, inches, or feet and inches before entering parent heights.

Mother height:

Example: 162 cm, 64 in, or 5 ft 4 in; converted value appears below.

ft in

Father height:

Example: 176 cm, 69.3 in, or 5 ft 9 in; converted value appears below.

ft in

Child sex:

Choose Girl or Boy for the target-height formula.

Target method:

Use Classic Tanner for 13 cm, UK Simple for 12.5 cm, or Adjusted for parent-centile regression.

Range preset:

Choose ±8.5 cm, ±10.2 cm, or Custom for a different band width.

Custom half-width:

Enter 4 to 15 cm; the same half-width is applied to all methods.

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Family height changes the meaning of a growth chart. A height centile that looks low beside classmates may fit a shorter family, while a child near the middle of the chart can still deserve attention if their growth has slowed or moved away from the family pattern. Parent heights do not replace serial measurements, but they give adult-height expectations a genetic reference point.

Mid-parental target height turns the adult heights of the biological mother and father into a same-sex adult-height midpoint for the child. The formula adds or subtracts a sex offset before averaging, or in adjusted methods, compares each parent with adult reference means and pulls the estimate partway toward the same-sex adult median.

The midpoint should be read with a band around it. Healthy children do not all finish at the exact family midpoint, and puberty timing, growth velocity, nutrition, chronic illness, and measurement quality can change how reassuring a number feels. The target is most useful when it is compared with a projected adult height or late-adolescent growth pattern, not with a single childhood height measurement.

Key ideas in mid-parental target height
Idea	Plain meaning	Common mistake
Parent heights	The family evidence used to frame adult-height potential.	Using remembered, rounded, or non-biological parent values without noting the limit.
Sex adjustment	The formula allowance for average adult height differences between males and females.	Applying a boy target to a girl, or the reverse.
Family band	A practical span around the midpoint for comparing projected adult height.	Focusing on one number and ignoring the expected range.
Growth pattern	The child's real measurements over time, including height velocity and centile changes.	Using family height as a substitute for serial measurements.

Measurement quality is a common source of false confidence. Parent heights should be measured adult heights when possible, not remembered or rounded values. A few centimeters of error in each parent can move the midpoint enough to matter near a family-band edge, and a large difference between parent heights makes any single midpoint feel less certain.

Family target height belongs beside the rest of the growth evidence. Age-specific growth charts, repeated height velocity, pubertal timing, bone age, nutrition, chronic disease, medicines, and physical exam findings can all change the clinical meaning of a height measurement. A family target can support a likely familial pattern, but it cannot diagnose growth failure or rule it out.

When a projected adult height falls well below the family band, when measurements cross centile lines, or when growth velocity slows unexpectedly, the target becomes a reason to look more closely. When the trajectory stays within the family band and growth is steady, the same calculation can help avoid overreacting to normal inherited stature.

How to Use This Tool:

Enter measured biological parent heights first, then choose the child's sex, formula method, and band width for the comparison you want to make.

Choose Height unit. Use centimeters, inches, or feet and inches before entering parent heights; the converted companion value below each parent field helps catch unit mistakes.
Enter Mother height and Father height. Each parent height must convert to 100 to 230 cm before the target results are shown.
If the message says parent heights should stay within 100 to 230 cm, check the selected unit before changing the actual height value.
Select Child sex. The simple formulas add the sex offset for a boy target and subtract it for a girl target, so the selected sex changes the midpoint.
Choose Target method. Classic Tanner uses a 13 cm offset, UK Simple uses 12.5 cm, and Parent-Centile Adjusted uses parent adult-height z-scores with regression toward the same-sex adult median.
Open Advanced only if the comparison needs a different range. 5th to 95th family span uses ±8.5 cm, 4-inch clinic span uses ±10.2 cm, and Custom half-width accepts 4 to 15 cm.
Changing Range preset changes the expected family band, not the selected target height.
Review Target Snapshot for selected target height, expected family band, approximate adult centile, parent spread, and method spread.
Check Formula Comparison, Interpretation Guide, and Family Height Map before sharing the result. The result is ready when units look correct, method spread is understood, and no validation message is visible.

Interpreting Results:

Selected target height is the midpoint from the chosen method. It is convenient to quote, but the Expected family band is usually the safer comparison. A projected adult height near the midpoint is reassuring only when the child's real measurements also show steady growth.

Approx adult centile places the selected midpoint on a same-sex adult reference distribution. It is not a child growth-chart centile and does not describe the child's height for their current age. Use it to understand where the family target sits among adults, not to replace age-based pediatric charting.

Parent spread shows how far apart the parent heights are. A larger spread makes the band more important because the midpoint is averaging two different adult statures. Method spread shows how much Classic Tanner, UK Simple, and Parent-Centile Adjusted disagree. Under 0.5 cm is effectively the same; 0.5 to under 2 cm is noticeable; 2 cm or more means formula choice changes the midpoint enough to mention.

A family-band result is not a clinical clearance. Height outside the band, growth that crosses centiles, slow growth velocity, unusual puberty timing, or symptoms that suggest nutrition, endocrine, chronic disease, or genetic causes should be reviewed with a qualified clinician.

Technical Details:

Mid-parental target height is a deterministic estimate from two adult parent heights. Heights are first converted to centimeters, then the selected method converts the parent pair into a same-sex adult target. The simple methods adjust the parent average by a fixed sex offset. The adjusted method works through standard deviation scores, so very tall or very short parent pairs are pulled partway back toward the same-sex adult median.

The family band is separate from the target midpoint. Changing band width expands or narrows the comparison span without changing the midpoint. That distinction matters because growth interpretation usually asks whether a projected adult height fits the family range, not whether it lands exactly on the midpoint.

Formula Core:

The formula depends on the chosen target method and the child's sex. Heights in inches or feet and inches are converted to centimeters before these equations are applied.

\begin{array}{lcl} boy simple target & = & \frac{H_{m} + H_{f} + O}{2} \\ girl simple target & = & \frac{H_{m} + H_{f} - O}{2} \\ parent z-score & = & \frac{H - μ}{σ} \\ adjusted target & = & μ_{s} + \frac{z_{m} + z_{f}}{4} \times σ_{s} \\ adult centile & = & Φ (\frac{T - μ_{s}}{σ_{s}}) \times 100 \end{array}

Mid-parental target height symbols and constants
Symbol or value	Meaning	How it is used
`Hm`	Mother height	Entered adult height converted to centimeters.
`Hf`	Father height	Entered adult height converted to centimeters.
`O`	Simple-method sex offset	13 cm for Classic Tanner; 12.5 cm for UK Simple.
`zm`, `zf`	Parent adult-height z-scores	Used by Parent-Centile Adjusted.
`μs`, `σs`	Same-sex adult reference mean and standard deviation	Girls: 162.9 cm and 7.0 cm; boys: 176.2 cm and 7.2 cm.
`T`	Selected target midpoint	The midpoint used for the family band and approximate adult centile.
`Φ`	Normal cumulative distribution function	Converts the same-sex adult z-score into a percentile-style centile.

With a 162 cm mother, 176 cm father, and girl target, the Classic Tanner midpoint is (162 + 176 - 13) / 2 = 162.5 cm. The ±8.5 cm preset gives an expected family band of 154.0 to 171.0 cm. The UK Simple offset moves the same example by only 0.25 cm because the offset changes from 13 cm to 12.5 cm before averaging.

Mid-parental target height boundaries
Boundary	Rule	Why it matters
Parent height	Each parent must be 100 to 230 cm after conversion.	Blocks implausible adult heights before they drive the estimate.
Default family span	±8.5 cm around each method target.	Matches a tighter family-height comparison often used in pediatric growth guidance.
Clinic span	±10.2 cm around each method target.	Matches the traditional 4-inch range on either side of the midpoint.
Custom half-width	Accepted from 4 to 15 cm.	Allows a different one-sided range while avoiding an unrealistically narrow or broad band.
Method spread	Under 0.5 cm, 0.5 to under 2 cm, or 2 cm and above.	Shows whether formula choice is trivial, noticeable, or material.
Approx adult centile	Calculated from same-sex adult mean and standard deviation.	Provides adult-population context, not a pediatric growth-chart result.

Accuracy, Privacy, and Safety Notes:

The calculation is only as good as the entered parent heights and the suitability of the chosen method. Rounding each parent height by a few centimeters can move the midpoint enough to matter near a band edge, especially when comparing a projected adult height against the family range.

Use measured adult biological parent heights when possible.
Do not use the adult centile as an age-based growth-chart centile for a child.
The calculation runs in the browser from the entered values; exported tables, images, documents, and JSON should be shared only with people who should see the family-height information.
Seek clinical review when height is far below or above family expectation, growth velocity slows, centiles are crossed, puberty timing is unusual, or other health symptoms are present.

Advanced Tips:

Use measured adult biological parent heights when possible. Rounded memories and old driver's-license heights can shift the midpoint by enough to matter near a band edge.
Compare the projected adult height from a growth chart with the Expected family band, not with the selected midpoint alone.
Use Method spread as a caution flag. When it reaches 2 cm or more, discuss the full band and method choice instead of quoting one exact value.
Use Parent spread to judge confidence. A large parent-height difference makes the band and adjusted estimate more informative than a single midpoint.
Keep exported values private. Parent heights and a child's expected adult range are family health information even when the calculation runs locally in the browser.

Worked Examples:

A family enters a 162 cm mother, 176 cm father, Girl, Classic Tanner, and the ±8.5 cm preset. Target Snapshot returns a selected target height near 162.5 cm and an expected family band of about 154.0 to 171.0 cm.

The same parent heights for a Boy with Classic Tanner move the midpoint to about 175.5 cm because the 13 cm sex offset is added instead of subtracted. Formula Comparison is the best place to see whether UK Simple or Parent-Centile Adjusted changes that result enough to matter.

A parent height entered as 90 cm triggers the message Parent heights should stay within a plausible adult range of 100 to 230 cm. Correcting the height or changing the unit restores Target Snapshot, Formula Comparison, Interpretation Guide, and Family Height Map.

FAQ:

Is mid-parental target height a prediction?

It is a family-height estimate, not a stand-alone prediction. It can frame growth discussions, but final adult height also depends on the child's real growth pattern, puberty timing, health, nutrition, and clinical context.

Which target method should I use?

Use Classic Tanner for the familiar 13 cm offset, UK Simple when a 12.5 cm offset is preferred, and Parent-Centile Adjusted when you want the parent z-score method shown beside the simple formulas.

Why does the family band change without changing the target?

Range preset changes only the half-width around the selected midpoint. It does not change Selected target height, Method spread, or the formula used.

What should I do if the input is rejected?

Check the selected Height unit and re-enter both parent heights. The calculation requires each parent height to land between 100 and 230 cm after conversion.

Glossary:

Mid-parental target height: A family-height midpoint estimated from biological parent adult heights and the child's sex.
Expected family band: The selected target midpoint plus and minus the chosen half-width.
Standard deviation score: A z-score showing how far a height is from a reference mean in standard deviation units.
Approx adult centile: The selected midpoint mapped to a same-sex adult reference distribution.
Growth velocity: The rate at which a child's measured height changes over time, usually read from repeated measurements.
Method spread: The distance from the lowest to highest target across the three available methods.

References:

Mid-parental Height, American Academy of Pediatrics EQIPP.
Growth Failure, Children's Mercy Kansas City.
Information for Health Staff, Royal College of Paediatrics and Child Health Digital Growth Charts.
Anthropometric Reference Data for Children and Adults: United States, 2015-2018, CDC National Center for Health Statistics.