This child height calculator predicts a child’s likely adult height from the parents’ heights using the mid-parental (target height) method pediatricians use — with the honest ± range genetics actually allows.
The Mid-Parental (Target Height) Method
Boy: (father + mother) ÷ 2 + 2.5 inches. Girl: (father + mother) ÷ 2 − 2.5 inches. Height heritability is high (~0.8 in well-nourished populations), so parental average anchors the prediction; the ±4-inch range (roughly ±2 SD, ~8.5 cm) contains the great majority of outcomes. Growth-clinic refinements (Khamis–Roche) add the child’s current height and weight — this calculator is the parents-only estimator, answering the question families actually ask. Part of our Health Calculators collection.
Worked Example (Verified)
- Father 5’10” (70″), mother 5’5″ (65″) (defaults): mid-parental = 67.5″ → son ≈ 5’10” (70″), daughter ≈ 5’5″ (65″) — the average sex difference reproduces the parents in this neat case
- Range honesty: that son plausibly lands 5’6″–6’2″ — a span wide enough to contain both a jockey build and a basketball build, which is why prediction is a range and destiny it is not
- Tall-mother/short-father pair (69″ & 72″): mid = 70.5 → son ≈ 6’1″, daughter ≈ 5’8″ — regression pulls extremes toward the mean less than folklore expects when both parents agree tall
What Else Moves the Needle
- Secular trend: well-documented ~1 cm/decade gains in many countries through the 20th century — children often outgrow the formula slightly where nutrition improved across generations.
- Early vs late maturation changes current percentiles, not (much) final height — late bloomers keep growing after early peers stop.
- Chronic illness, malnutrition and some medications can hold a child below their genetic channel; a growth curve crossing channels downward is the pediatric red flag, not a single short measurement.
- The “double the height at age 2” rule of thumb (boys; 18 months for girls) gives a rougher estimate — typically within ~2 inches of the mid-parental figure.
Related Tools
- Ideal Body Weight Calculator — what the charts say about the adult result
- Conception Calculator — the timeline at the other end
- Health Calculators — the full collection
Frequently Asked Questions
How do you predict a child’s adult height?
Mid-parental method: average the parents’ heights, add 2.5 inches for a boy or subtract 2.5 for a girl. Parents at 70″ and 65″ predict a son near 5’10” and a daughter near 5’5″ — with a ±4-inch expected range around each.
How accurate is the mid-parental prediction?
The ±4-inch band captures roughly 95% of outcomes in healthy populations — accurate as a family-planning expectation, useless as a promise. Methods adding the child’s current size (Khamis–Roche) narrow the error to about ±2 inches for ages 4+.
Can a child outgrow both parents?
Yes, routinely — each parent carries recessive “tall” and “short” variants the child can recombine, nutrition improved between generations, and the ± range extends above the taller parent in many cases. Regression to the mean tempers, not caps.
When do girls and boys stop growing?
Girls typically reach adult height by 14–16 (about 2 years after periods begin), boys by 16–18, with late maturers adding small amounts into their early 20s. Growth plates, assessed by a hand X-ray (bone age), give the definitive answer.
Should I worry if my child is short for the prediction?
Track the curve, not the point: a child growing steadily along a low channel consistent with family heights is usually a healthy pattern. Falling across percentile channels, or height far below the target range with other symptoms, is what pediatricians investigate — bring the growth chart, not just the calculator.
Is this child height calculator free?
Yes — free, instant, no sign-up.