Child Height Predictor

How Predicted Adult Height Is Calculated

The mid-parental height method estimates a child’s likely adult height by averaging both parents’ heights and adjusting for the child’s gender at birth — a long-standing pediatric formula, not something invented for this calculator. Enter both parents’ heights and the child’s gender at birth, and this calculator shows the predicted adult height plus the commonly-cited range most children actually fall within.

This method (popularized by growth researcher J.M. Tanner) works from birth onward, since it only needs the two parents’ own heights — not the child’s current height or bone age, which other, more involved prediction methods use instead.

The Formula

$$\text{Predicted Height} = \frac{\vA{\text{Mother's Height}} + \vB{\text{Father's Height}} \pm \vC{13\text{ cm}}}{2}$$

The adjustment is added for a boy and subtracted for a girl — reflecting the roughly 13 cm average adult height difference between men and women that this method assumes.

Worked Example

A mother who is 165 cm tall and a father who is 180 cm tall, expecting a boy:

1. $(165 + 180 + 13) \div 2 = 179$ cm predicted adult height.
2. Likely range (about 68% of children): 170.5–187.5 cm.
3. Wider range (about 95% of children): 162–196 cm.

For a girl with the same parents: $(165 + 180 - 13) \div 2 = 166$ cm.

Key Factors to Consider

• This method assumes both biological parents’ heights are accurately known. The formula’s accuracy depends entirely on entering the biological parents’ own genuine adult heights — a height that includes shoes, or a measurement taken years ago before further growth, will skew the result.
• Genetics from both parents combine in complex ways beyond a simple average. Height is influenced by many genes, not a single trait that averages cleanly — this is exactly why the method reports a range rather than a single number, since two children with the same parents can still land at meaningfully different points within that range.
• Nutrition and overall childhood health can shift a child away from their genetic potential. Chronic illness, malnutrition, or other significant health factors during childhood can prevent a child from reaching the height this genetics-based estimate predicts — the formula assumes reasonably normal health and nutrition throughout childhood.
• This method predates modern statistical and genetic height-prediction research, but remains widely used for its simplicity. More sophisticated methods exist (some incorporating a child’s own bone age or growth velocity), but the mid-parental height method remains a standard, easy first-pass estimate precisely because it needs no data beyond the parents’ own heights.

Common Mistakes

• Treating the point estimate as a guarantee. This is a population-level average, not a measurement — the ranges above exist precisely because individual children vary meaningfully around the estimate.
• Expecting precision down to the centimeter. Even the “likely” range spans 17 cm (about 8.5 cm each direction) — this is a ballpark for planning purposes, not a clinical growth assessment.
• Using this instead of a pediatrician’s own growth-chart tracking. A doctor tracking a child’s own height and growth velocity over time on age-specific percentile charts has real, individual data this formula doesn’t — it’s a much better source once a child is old enough to track.

Useful to Know

Once a child is a few years old, a pediatrician can use more accurate methods that incorporate the child’s own current height and growth pattern, and — if there’s a specific medical concern — a bone-age X-ray, which reads how much growth plate remains and narrows the predicted range far more than parental heights alone can. Mid-parental height’s real advantage is that it needs nothing but the two biological parents’ own heights, so it works from before birth onward, long before any of those more involved methods have anything to measure.