Child Height Predictor
The mid-parental height formula combines both parents' heights with a gender correction factor to estimate a child's likely adult height. It reflects the genetic contribution to height and is widely used by pediatricians as a first-line prediction tool.
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Formula
Boy = (Father + Mother + 5) ÷ 2; Girl = (Father + Mother − 5) ÷ 2
The mid-parental method averages both parents' heights in the same units and applies a ±2.5 inch adjustment per parent to account for the average height difference between adult males and females (~5 inches). Adding 5 inches then halving targets the mid-point of the male height distribution relative to the parents; subtracting 5 inches targets the female distribution. The predicted height is a central estimate — actual height falls within ±2 inches of this prediction for roughly two-thirds of children.
How to use the Child Height Predictor
- 1
Enter your father's height
Value should be in inches.
- 2
Enter your mother's height
Value should be in inches.
- 3
Enter your child's gender
- 4
Read your results instantly
Results update in real time as you type.
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How accurate is the mid-parental method
The mid-parental formula predicts adult height within ±2 inches (~5 cm) for approximately two-thirds of children. The remaining third will fall outside that range due to variation in genetic expression, environmental factors, nutrition, and the influence of grandparents and other ancestors beyond the immediate parents. Children with a very tall parent and a very short parent have higher prediction uncertainty than children of parents with similar heights. Pediatric growth charts tracking a child's percentile over time provide more individualized prediction than this formula alone.
Factors that affect adult height
Genetics accounts for approximately 80% of adult height variation. Nutrition during childhood and adolescence — particularly adequate protein, calcium, and total calories — is the most important environmental factor. Chronic illness, hormonal conditions (growth hormone deficiency, hypothyroidism), and prolonged use of corticosteroids can all significantly reduce adult height below genetic potential. Conversely, excellent nutrition during growth years allows children to reach the upper range of their genetic potential. Sleep is also important — growth hormone is primarily secreted during deep sleep.
Tips & Insights
The ±2 inch range is a confidence interval
Treat the result as the center of a ±2 inch range rather than a precise prediction. For example, a prediction of 68 inches means the likely range is 66–70 inches.
Bone age X-ray is more precise
A hand/wrist X-ray allows a radiologist to assess bone maturity and provide a more precise adult height prediction, particularly useful when a child is growing significantly faster or slower than peers.
Nutrition in early childhood matters enormously
Children who are undernourished in the first 1000 days (conception to age 2) often do not reach their genetic height potential. Adequate protein and micronutrient intake during growth years is critical.
Worked Examples
Father 72", mother 64", boy
Predicted height ≈ 70.5" (179 cm)
Father 68", mother 62", girl
Predicted height ≈ 62.5" (159 cm)
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Frequently Asked Questions
How accurate is this formula for mixed-ethnicity families?
The mid-parental method is population-agnostic in that it uses parents' actual heights. Ethnic height differences are captured implicitly in the parents' measurements.
At what age do boys stop growing?
Most boys complete their height growth by 17–18, with some continuing until age 21. The growth spurt peaks around 13–15 during puberty.
At what age do girls stop growing?
Most girls complete height growth by 15–16, typically 2–3 years after the onset of menstruation. Growth plates generally fuse earlier in females than males.
Can a child grow taller than this prediction?
Yes. Approximately one-sixth of children will be more than 2 inches taller than their mid-parental prediction. Grandparent heights, de novo growth variants, and favorable nutrition all contribute to exceeding the prediction.
Is there anything I can do to maximize my child's height?
Ensure adequate sleep (growth hormone peaks during deep sleep), provide protein-rich nutrition, treat any chronic illnesses promptly, and avoid unnecessary corticosteroid use. These optimize height within the genetic potential rather than exceeding it.
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