What this calculator does
The Child Height Prediction Calculator estimates a child's likely adult (final) height from the heights of the two biological parents. It uses the classic mid-parental height method, also called the target-height formula, which is widely used by clinicians and growth charts around the world. This is a generic anthropometric estimate, not a country-specific rule, and all heights are entered in centimeters.
How to use it
Choose whether the child is a boy or a girl, then enter the father's height and the mother's height in centimeters. Click calculate and the tool returns one predicted adult height. If you only have heights in inches, multiply each by 2.54 to convert to centimeters before entering them.
The formula explained
First add the two parent heights together: \(S = \text{Father} + \text{Mother}\). Then apply the sex adjustment. For a boy: $$\text{Predicted} = \frac{S + 13}{2} + 2.$$ For a girl: $$\text{Predicted} = \frac{S - 13}{2} + 2.$$ The 13 cm term reflects the average adult height difference between men and women, and the trailing +2 is an adjustment constant. Halving the adjusted sum gives the mid-parental value.
Worked example
Suppose the child is a boy, the father is 175 cm and the mother is 160 cm. The sum \(S = 175 + 160 = 335\). $$\text{Predicted} = \frac{335 + 13}{2} + 2 = \frac{348}{2} + 2 = 174 + 2 = 176 \text{ cm}.$$ For a girl with a 177 cm father and 170 cm mother: \(S = 347\), $$\text{Predicted} = \frac{347 - 13}{2} + 2 = \frac{334}{2} + 2 = 169 \text{ cm}.$$
FAQ
How accurate is this prediction? It is only a guideline. Real adult height can vary by several centimeters in either direction because of nutrition, health, puberty timing and individual genetic variation.
What units should I use? Centimeters. Convert inches to cm by multiplying by 2.54.
Why is there a +2 constant? It is a small secular adjustment built into this version of the target-height formula to better match observed final heights.
