Child Height Predictor Calculator

How This Calculator Works

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.

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.