Children’s Adult Height
Prediction Calculator
Estimate your child’s adult height using three science-based prediction methods — mid-parental formula, linear regression, and percentile projection — with a personalised growth chart.
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Children’s Adult Height Prediction Calculator
“How tall will my child be?” is one of the most common questions parents ask paediatricians — and while no calculator can predict adult height with certainty, several well-validated scientific methods provide useful estimates. This free child height predictor uses three approaches: the mid-parental height formula (the most widely cited genetic method), a current-growth linear projection based on CDC/WHO reference data, and a percentile-based projection using your child’s most recent growth chart measurement.
Quick example: A boy with a 178 cm father and 165 cm mother has a mid-parental predicted height of (178 + 165 + 13) ÷ 2 = 178 cm, with a typical range of 169.5–186.5 cm. For a girl with the same parents: (178 + 165 − 13) ÷ 2 = 165 cm (range 156.5–173.5 cm). Enter your values above for your child’s personalised prediction.
How Adult Height Prediction Works
Height prediction is an estimation science, not an exact calculation. It relies on the strong statistical relationship between parental heights and child adult height — a relationship driven by the polygenic inheritance of hundreds of genetic variants that influence skeletal growth, growth hormone signalling, and pubertal timing.
Several validated clinical methods exist, each with different data requirements and accuracy characteristics. This calculator implements three:
Mid-Parental Height (Method 1)
Published by Tanner et al. (1966) and refined by multiple subsequent studies. Uses only parental heights. Accuracy: predicts adult height within ±8.5 cm for 95% of children. Most useful for infants and young children where current growth data has limited predictive power.
Current Growth Projection (Method 2)
Based on the principle that children tend to track along a consistent height percentile from age 2 onward. Uses the child’s current height relative to CDC growth chart 50th percentile reference values to estimate their adult percentile position. Most accurate for children who have established a stable growth track (age 4+).
Percentile Projection (Method 3)
Uses an established percentile from a recent clinical visit. Projects the same percentile rank to adulthood using the adult height distribution. Appropriate when you have a trusted percentile from your child’s paediatrician and want to understand what that percentile means for final adult height.
Bone Age Radiograph (Clinical Method)
The most accurate clinical prediction method — a hand/wrist X-ray determines skeletal maturity (“bone age”), which is compared to chronological age. Bone age predictions (Bayley-Pinneau tables) are accurate to ±2.5 cm in pubescent children. This requires a clinical referral and is used when growth concerns exist.
The Mid-Parental Height Formula Explained
Formula (metric):
For boys: (Father’s height + Mother’s height + 13 cm) ÷ 2
For girls: (Father’s height + Mother’s height − 13 cm) ÷ 2
The ±13 cm correction accounts for the average height difference between adult males (175.5 cm) and females (162 cm) — a 13.5 cm difference. The formula produces the “mid-parental height target” — the child’s genetically expected adult height assuming average nutritional and health conditions.
Confidence interval: 95% of children grow to within ±8.5 cm of this target. This means if the mid-parental prediction is 175 cm, the child is expected to grow to between 166.5 cm and 183.5 cm with 95% probability.
How the Height Prediction Calculator Formula Works
This calculator measures a statistical estimate of a child’s future adult height, using one of three inputs depending on which method you choose: both parents’ heights, the child’s current age and height, or an established growth percentile. Each method produces a predicted height in centimetres, plus a range reflecting the natural uncertainty in that method. Read the predicted number as the centre of a probability range, not a guarantee. The formula assumes the inputs are accurate and that the child’s growth continues along a broadly typical pattern; conditions that affect growth timing, such as early or delayed puberty, will shift the actual outcome away from any of these estimates.
Identify the inputs
For the Mid-Parental method, you enter both parents’ heights and the child’s sex. The other two methods use current age and height, or a known percentile instead.
Apply the formula
For boys: (father’s height + mother’s height + 13) ÷ 2. For girls: (father’s height + mother’s height − 13) ÷ 2. The result becomes the centre of a range spanning ±8.5 cm.
Perform the calculation
Using the calculator’s default example: a boy with a 178 cm father and 165 cm mother. (178 + 165 + 13) ÷ 2 = 356 ÷ 2 = 178 cm.
Interpret the result
178 cm is the statistically expected adult height, with the calculator showing a range of 169.5 to 186.5 cm covering 95% of children with these parental heights.
3 Real-Life Examples
1. Mid-Parental Height for taller-than-average parents
A father is 190 cm and a mother is 175 cm, and they want an estimate for their son, using the Mid-Parental Height method.
The estimated range is 180.5 to 197.5 cm. Because both parents are above average height, the mid-parental target sits well above the average adult male height of 175.5 cm, reflecting the strong genetic component of height.
2. Current Growth Projection for a shorter-than-average boy
A 6-year-old boy is 110 cm tall, below the CDC 50th percentile of 116 cm for his age, and his parents want to know what that trajectory implies for adult height, using Current Growth Projection.
The estimated range is 157.4 to 175.4 cm. This method assumes he continues tracking at roughly the same relative position on the growth curve, which tends to hold reasonably well for children past the toddler years who haven’t yet entered puberty.
3. Percentile Projection using a paediatrician’s chart reading
A 10-year-old boy was measured at the 90th percentile for height at his last check-up, and his parents want to understand what that means for his adult height, using Percentile Projection.
The estimated range is 175.8 to 191.8 cm. This method is most reliable when the percentile comes from a recent, accurate clinical measurement rather than an estimate, since it projects that exact percentile rank forward to adulthood.
Growth Percentiles: What They Mean
| Percentile | What it means | Action needed? |
|---|---|---|
| Below 3rd | Taller than only 3% of children same age/sex | Paediatrician consultation recommended |
| 3rd–15th | Below average but within normal variation | Monitor; discuss with paediatrician if declining |
| 15th–85th | Normal healthy range | No action needed |
| 85th–95th | Above average; within normal variation | No action needed |
| Above 95th | Taller than 95% of same-age peers | Usually normal; may warrant monitoring |
A child’s percentile ranking is more meaningful than the absolute height — it shows where they sit relative to their peers of the same age and sex. A child consistently at the 25th percentile is not “short” — they are exactly where they are genetically expected to be. Concern arises when percentiles cross significantly (dropping from the 50th to the 10th) or when a child falls outside the 3rd–97th percentile range.
Important Notes
What this calculator does and doesn’t cover
This tool applies standard statistical growth-prediction formulas to the numbers you enter. A few things worth understanding before relying on the results:
- Each method has a different, method-specific margin of error, shown in the range alongside the prediction: ±8.5 cm for Mid-Parental Height, ±9 cm for Current Growth Projection, and ±8 cm for Percentile Projection. None of these ranges guarantee the actual adult height.
- The Current Growth and Percentile methods reference CDC 50th percentile data for children aged 2 to 18. See the CDC’s official growth charts for the full reference curves these figures are drawn from.
- Predictions become more reliable as a child gets older, particularly once a stable growth percentile is established (usually by age 4 to 5), and again once puberty timing becomes clearer.
- Environmental factors matter alongside genetics. Chronic malnutrition, untreated illness, or significant health conditions during childhood can shift actual adult height meaningfully below any of these statistical predictions.
- Not a diagnostic tool. This calculator cannot detect growth hormone deficiency, genetic growth disorders, or other medical causes of unusually short or tall stature. If you have concerns about your child’s growth, a paediatrician can assess bone age and other clinical markers that this tool has no access to.
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