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How Child Height Predictor (Based on Parents) works
The Child Height Predictor uses the clinically validated Mid-Parental Height (MPH) formula, also known as the Tanner method, to estimate an adult child's predicted height based on both biological parents' heights. This method is widely used by paediatricians as a first-line genetic height estimate and is taught in clinical medicine curricula worldwide.
For boys, the formula averages both parents' heights and adds 6.5 cm (2.5 inches) to account for the male sex's typically taller stature. For girls, the formula averages both parents' heights and subtracts 6.5 cm (2.5 inches). The result is the Mid-Parental Height — the child's predicted adult height. Clinical studies have shown that approximately 85–95% of children reach an adult height within ±8.5 cm (±3.35 inches) of this predicted value, which is presented as the target height range.
This tool also supports optional current height and age inputs to place the child on a simplified percentile curve, showing how current growth trajectory compares to the genetic height estimate and population norms.
How to use Child Height Predictor (Based on Parents)
1. Enter both parents' heights
Input the biological mother's and father's adult heights. Use the unit toggle to switch between centimetres and feet/inches.
2. Select the child's sex
Choose Boy or Girl. The Mid-Parental Height formula applies a ±6.5 cm (±2.5 in) sex-adjustment factor to account for average stature differences between males and females.
3. Review the predicted height and range
The calculator displays the child's Mid-Parental predicted height, the ±8.5 cm (±3.35 in) 95% target range, and a side-by-side height comparison bar chart with both parents and the predicted adult child height.
4. (Optional) Enter current age and height
For children still growing, input their current age and measured height to see how their current growth compares to the genetic prediction and population percentile curves.
Key features and technical specifications
Tanner Mid-Parental Height Formula
Uses the clinically standard MPH formula — the same method paediatricians use as a first-line genetic height reference — with sex-specific ±6.5 cm adjustment.
Target Height Range (85–95% CI)
Displays the predicted height alongside the ±8.5 cm / ±3.35 in target range that captures approximately 85–95% of children.
Visual Height Comparison Chart
Side-by-side bar chart comparing mother, father, and predicted child heights for intuitive visual reference.
Units Toggle (cm / ft-in)
Seamlessly switch between metric (centimetres) and imperial (feet and inches) for all height inputs and outputs.
100% Private — No Data Transmitted
No parents' or children's biometric data is uploaded or stored. All calculations run locally in JavaScript within your browser.
Growth trends matter more than a single estimate
Measure both parents in the same units and check that feet and inches have not been entered as decimal feet. A parental-height formula describes a broad family pattern. It does not use a child’s growth velocity, pubertal development or clinical history. Discuss concerns about growth with a clinician who can interpret measurements over time.
Paediatric growth monitoring
Parents and paediatricians can compare a child's current height trajectory against the genetic target range to identify potential growth concerns early.
Curiosity and family planning conversations
Estimate expected heights for future children based on both parents' heights to satisfy natural family curiosity about inherited traits.
Sports and activity planning
Estimate final adult height to inform long-range planning decisions related to sport selection, equipment sizing, or scholarship projections in height-advantaged athletics.
Frequently asked questions
How accurate is the Mid-Parental Height formula?
The Tanner Mid-Parental Height method is well-validated as a first-line clinical estimate. Studies show approximately 85% of children reach an adult height within ±8.5 cm (±3.35 in) of the predicted MPH. However, it accounts for genetic contribution only. Nutrition, chronic illness, hormonal conditions (e.g., growth hormone deficiency), pubertal timing, and epigenetic factors also substantially influence final adult height.
What is the Mid-Parental Height (MPH) formula?
For boys: MPH = (Father's height + Mother's height + 13 cm) ÷ 2. For girls: MPH = (Father's height + Mother's height − 13 cm) ÷ 2. In imperial units, 13 cm ≈ 5 inches. The resulting MPH is the best single-number genetic estimate of a child's adult height.
Why does the child's sex affect the predicted height?
The male sex-adjustment factor (+13 cm / +5 in for boys, −13 cm / −5 in for girls) normalises both parents' heights to the same sex before averaging, accounting for the fact that males are statistically taller than females on average. Without this adjustment, using a father's height of 180 cm and a mother's height of 165 cm would underestimate a son's genetic potential and overestimate a daughter's.
Can I use this for adopted children?
The formula requires the heights of both biological parents. For adopted children whose biological parents' heights are unknown, the formula cannot produce a meaningful estimate. In such cases, paediatric growth charts and serial height measurements plotted over time provide the most clinically useful information.
At what age does height growth stop?
In most individuals, significant height growth ceases after the closure of epiphyseal growth plates — typically 16–18 years for females and 18–21 years for males. This is largely regulated by oestrogen (which triggers plate fusion regardless of sex) and growth hormone. Minor height changes may continue into early adulthood in late-maturing individuals.
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