Projected Adult Height Calculator
Estimate projected adult height from child height, age, sex, and parent heights with range, percentile, and family-band checks.{{ summary.title }}
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Introduction:
Adult-height projection is best read as a growth conversation, not a promise about a final number. A child's current standing height says where they are today. A growth reference says how that height compares with children of the same age and sex. Biological parent heights add a family pattern. The useful estimate comes from seeing whether those clues point in the same direction.
Percentiles are comparison ranks. A child at the 50th percentile is near the middle of the selected reference group for age and sex. A child at the 5th percentile is shorter than most peers in that reference group, and a child at the 95th percentile is taller than most peers. Neither number is automatically good or bad. The bigger concern is a height that is far outside the family pattern, changes percentile lanes quickly, or appears with unusual puberty timing, illness, nutrition concerns, or other symptoms.
| Clue | What it contributes | Common mistake |
|---|---|---|
| Recent standing height | Places the child on an age-and-sex reference curve. | Trusting one casual or mismeasured height as exact. |
| Growth history | Shows whether the child is following a familiar lane or crossing percentiles. | Projecting from one visit without checking earlier measurements. |
| Parent heights | Gives a rough genetic target through mid-parental height. | Expecting the child to land exactly at the family midpoint. |
| Age and puberty timing | Changes how much growth may remain. | Comparing early and late maturers as if they have the same remaining growth. |
Mid-parental height is a simple family-height estimate. It averages biological parent heights after applying a sex-specific adjustment, then treats the result as a broad target, not a guaranteed endpoint. It can explain why a shorter child may still fit a shorter family pattern or why a tall child may fit tall parents, but it cannot account for bone age, chronic disease, endocrine conditions, nutrition, medications, or the exact timing of puberty.
Projected height ranges are useful when they shape the next step: repeat a questionable measurement, compare growth over time, discuss family-height fit, or decide whether a pediatric review is warranted. The range should be quoted with the assumptions that produced it, especially when current percentile and parent-height target pull in different directions.
A projection should not replace clinical review when the child is very short or very tall for age, crossing percentiles, outside the expected family range, showing unusually early or delayed puberty, or causing persistent concern. In those cases, the more useful evidence is a reliable plotted growth record, repeat measurement, puberty and health history, and professional assessment.
How to Use This Tool:
Start with accurate standing heights and the child's completed age. Then compare the projection midpoint, range, family band, and scenario spread before sharing the result.
- Choose Height unit first. The height fields accept centimeters, inches, or feet plus inches, and switching units keeps the underlying height consistent.
- Enter Mother height and Father height as biological adult standing heights when known. Both are needed for the Family target midpoint and Family target band.
- Select Child sex, then enter Child age from 2y 0m through 17y 0m and the child's Current height. Validation messages name the age or height field that needs correction.
- Use Growth reference set to choose the comparison lens. Hybrid continuity model is the default, while WHO-style and CDC-style settings test a different reference emphasis.
- Choose Projection method mode. The age-weighted blended model combines current percentile with the family target, Percentile tracking only removes the family pull, and Family-target anchor gives parent heights more influence.
- Set Family target band if the family-fit check needs a narrower or wider half-width. The supported range is 4 to 15 cm, with 8.5 cm as the default.
- Open Advanced for optional Current weight, Projection blend override, Puberty timing offset, or action-guide wording. Weight adds BMI-for-age context only; it does not change the projected adult height.
- Read Projection Snapshot first, then compare Projection Scenarios, Interpretation Guide, Action Guide, and Projection Path Chart. When scenario rows disagree, quote the range and Scenario spread before the midpoint.
Interpreting Results:
The main result is the relationship between Blended projected adult height, Projected range, Current height percentile, Family target band, and Scenario spread. A midpoint inside the family band with a small scenario spread is easier to use than a midpoint that moves several centimeters when method or puberty timing changes.
Do not overread one decimal place. A small measurement error, a unit mix-up, or a wrong age entry can move the z-score and the adult endpoint. If the estimate is surprising, first recheck Current height, Child age, and parent heights, then look at Track vs family midpoint gap and Family band fit.
- Inside family target band means the projected midpoint is within the selected half-width around the mid-parental target.
- Scenario spread of 4 cm or less is treated as stable; above 8 cm, the range should carry more weight than the midpoint.
- Current height percentile below the 3rd or above the 97th percentile raises the action priority.
- BMI-for-age context, when entered, describes body-size context only. It does not alter the height projection formula.
Technical Details:
Projected adult height combines a current growth-chart position with a family-height target. The growth-chart side converts today's standing height into a z-score against the selected age-and-sex reference, then applies that same standard-deviation position to an adult same-sex reference. The family side calculates a mid-parental target using the two biological parent heights and a 13 cm sex adjustment.
The reference setting adjusts the median and spread used for height and optional BMI context. WHO-style and CDC-style settings are simplified lenses around the same projection method, not official chart table output. The estimate is deterministic for the entered values, but growth itself remains uncertain because bone age, growth velocity, puberty stage, chronic health conditions, and measurement history are not fully represented by one current height.
Formula Core:
All height equations use centimeters after any inch or feet-plus-inches entry has been converted.
| Symbol | Meaning | Unit or rule |
|---|---|---|
| z | Current height expressed as standard deviations from the selected reference median. | Unitless |
| Htrack | Adult height from carrying today's z-score to the adult same-sex reference. | cm |
| Hfamily | Mid-parental target. Add 13 cm for boys and subtract 13 cm for girls before dividing by 2. | cm |
| w | Percentile-track share of the blend. Automatic mode uses age anchor divided by 180, clamped from 0.35 to 0.90. | 0 to 1 |
| BMI | Optional body mass index, computed as weight divided by height in meters squared. | kg/m2 |
Percentile-only mode sets the blend weight to 1. Family-target anchor mode uses a 0.35 percentile-track share unless a manual blend override is active. If parent heights are unavailable, the projection falls back to percentile tracking because there is no family target to blend with.
The puberty timing offset shifts the age anchor by -24 to 24 months before automatic blend and range logic are calculated. The displayed range starts from an age-based uncertainty term, grows when the percentile-track adult estimate disagrees with the family target, grows when a puberty offset is applied, and adds a small bump when a manual blend override is active. The final range half-width is clamped from 3.5 to 9.8 cm.
| Check | Boundary | Effect on interpretation |
|---|---|---|
| Supported child age | 24 to 204 months inclusive | Outside this range, the projection is not produced until the age is corrected. |
| Current standing height | 70 to 220 cm inclusive | Out-of-range values are treated as unrealistic for this estimate. |
| Parent heights | Mother 120 to 220 cm; father 130 to 235 cm when entered | Out-of-range parent heights stop the family-target calculation until corrected. |
| Family target band | 4 to 15 cm half-width | The projected midpoint is compared with target minus band through target plus band. |
| Current percentile flag | < 3rd, 3rd to < 10th, 10th to < 90th, 90th to < 97th, and > 97th |
Very low or very high percentiles increase action priority. |
| Scenario stability | <= 4 cm, <= 8 cm, or > 8 cm spread |
Larger spread means assumptions matter more than the midpoint. |
With the default example, a 10-year-old girl at 138 cm is near the middle of the hybrid height lane. Parent heights of 162 cm and 176 cm give a family target midpoint of 162.5 cm. The percentile-track adult estimate is about 164.5 cm, and the age-weighted blend lands near 163.8 cm with a projected range of about 157.4 to 170.2 cm.
The path chart extends the current percentile estimate toward adulthood, adds a reference line, and marks the family target band plus current, earlier-timing, and later-timing endpoints. Calculations keep more precision internally, while displayed heights are usually rounded to one decimal place.
Accuracy Notes:
This is an informational growth estimate, not medical advice, diagnosis, or treatment guidance. It cannot replace a pediatric growth chart review, repeated accurate measurements, pubertal staging, bone-age assessment, or clinician judgment.
- Use standing height measured without shoes, preferably from a recent growth visit.
- Repeat the estimate after reliable new measurements instead of relying on one casual height entry.
- Seek professional review for very low or very high percentiles, rapid percentile crossing, delayed puberty, early puberty, chronic illness, or persistent concern.
Worked Examples:
Typical school-age estimate. A 10-year-old girl is 138 cm, with parent heights of 162 cm and 176 cm. Projection Snapshot reports a current height percentile near the middle of the reference lane, a Family target midpoint near 162.5 cm, and Blended projected adult height near 163.8 cm. A small Scenario spread supports quoting the range with moderate confidence.
Family target pulls upward. A 13-year-old boy at 160 cm with parent heights of 165 cm and 180 cm has a percentile-tracking adult estimate below the family target. The blended result sits between those two signals, while Family-target anchor moves closer to the parent midpoint. The Track vs family midpoint gap should be discussed before quoting one future height.
Input needs review. If child age is entered as 18 years, it falls outside the 24 to 204 month range. If current height is typed as 22 cm instead of 122 cm, the realistic-height check stops the estimate. Fix the unit or number first, then confirm that Current height percentile looks plausible.
FAQ:
Why does the estimate show a range?
Adult height depends on measurement quality, growth timing, and agreement between current percentile and family target. The Projected range keeps that uncertainty visible.
What if I do not know both parent heights?
The family target becomes unavailable, so the estimate relies on percentile tracking. The result can still be useful, but Family band fit cannot judge parent-height alignment.
Does current weight change projected adult height?
No. Current weight only adds BMI-for-age context. It does not change the height percentile, family target, projected midpoint, range, or scenarios.
Why do puberty timing settings move the result?
The Puberty timing offset changes the age anchor used for blend weight and range width. Earlier or later timing can change how strongly current percentile influences the endpoint.
Why did I get a realistic-range error?
The page checks child age, current height, parent heights, and optional weight against broad supported ranges. Recheck centimeters versus inches or feet plus inches first, then correct the field named in the message.
Glossary:
- Height percentile
- A comparison rank against children of the same age and sex in the selected reference lane.
- z-score
- The number of standard deviations a child's height sits above or below the selected median.
- Mid-parental target
- A rough family-height midpoint calculated from biological parent heights with a sex-specific 13 cm adjustment.
- Scenario spread
- The distance between alternate adult-height endpoints created by method and puberty-timing assumptions.
- BMI-for-age
- Body mass index interpreted by age and sex; here it is optional context, not a direct adult-height predictor.
References:
- Growth Charts, Centers for Disease Control and Prevention.
- Plotting and Interpreting BMI-for-Age, Centers for Disease Control and Prevention.
- Growth reference data for 5-19 years, World Health Organization.
- Predicting a Child's Adult Height, HealthyChildren.org, American Academy of Pediatrics.
- Evaluation of Short and Tall Stature in Children, American Family Physician.