About Height Prediction
“How tall will my kid be?” has three grades of answer: the parent-based formula here (instant, ballpark), percentile-tracking on growth charts (a child who rides the 75th percentile usually finishes near it), and bone-age X-ray assessment (the clinical gold standard when it medically matters). This tool delivers the first — honestly labeled.
Enter both parents' heights and the child's sex for the estimate and its likely range. Siblings share the same mid-parental number yet routinely land several centimeters apart — that's the ±8.5 cm band doing exactly what it says.
Tracking where a child stands against peers right now? That's the Height Percentile Calculator.
The Mid-Parental Formula
One average, one sex offset:
Boy: (mother + father) ÷ 2 + 6.5 cm Girl: (mother + father) ÷ 2 − 6.5 cm Likely range: estimate ± 8.5 cm (± 3.3 in)
Worked example: mother 165 cm, father 180 cm → mid-parental 172.5. A son estimates 179 cm (5′10″), range 171–188; a daughter 166 cm (5′5″), range 158–174. The 13 cm gap between the two estimates is the average adult sex difference — the formula's entire adjustment.
Example Predictions
The formula across common parent combinations (computed by this calculator):
| Mother | Father | Son (est.) | Daughter (est.) |
|---|---|---|---|
| 155 cm (5′1″) | 170 cm (5′7″) | 169 cm (5′7″) | 156 cm (5′1″) |
| 160 cm (5′3″) | 175 cm (5′9″) | 174 cm (5′9″) | 161 cm (5′3″) |
| 165 cm (5′5″) | 180 cm (5′11″) | 179 cm (5′10″) | 166 cm (5′5″) |
| 170 cm (5′7″) | 185 cm (6′1″) | 184 cm (6′0″) | 171 cm (5′7″) |
| 175 cm (5′9″) | 190 cm (6′3″) | 189 cm (6′2″) | 176 cm (5′9″) |
Every cell carries the same silent ±8.5 cm — reading the table without the range is how formulas get oversold.
What Moves the Outcome
Within the genetic range, the levers are unglamorous: adequate nutrition (the reason average heights climbed a full head over the last century in many countries), managed chronic conditions, and sleep — growth hormone pulses strongest in deep sleep. Puberty timing shifts the schedule more than the destination: early bloomers spurt sooner and stop sooner; late bloomers keep growing after peers plateau.
When prediction turns clinical: a child crossing percentile lines downward on the growth chart, sitting far below the parental range, or showing very early/late puberty warrants a pediatric conversation — bone-age assessment separates 'late bloomer' from conditions worth treating. For the record, the other folk formula (doubling height at age 2, or 18 months for girls) is a rougher cousin of the same idea — the growth chart beats both.