This calculator estimates a child's adult height and converts height between US and metric units. The child tabs use the Khamis–Roche method (current height, weight, age, sex, and both parents). The parents-only tabs use the simpler mid-parental formula, which is useful before birth. Results are educational estimates, not a diagnosis.
Formula
Khamis–Roche (child tabs)
At each half-year of age from 4.0 to 17.0, adult height in inches is a linear regression on current stature, weight, and mid-parental height:
adult height (in) = B₀ + b₁ × height (in) + b₂ × weight (lb) + b₃ × mid-parent (in)
Mid-parent is (mother + father) / 2. Coefficients are sex-specific and come
from the 1995 erratum to Khamis & Roche, Pediatrics 1994. calculator.net
rounds each half-year knot to a whole inch, then interpolates for ages in
between. From 17.5 to 18 the prediction is the child's current height. Under
4, a mid-parental stand-in round(mid-parent ± 3 in) is used, then blended
into the age-4 knot.
Metric entries convert with 1 in = 2.54 cm and 1 lb = 0.45359237 kg; the interpolated inches are converted back and rounded to a whole centimetre.
Mid-parental / Tanner (parents-only tabs)
boy = (mother + father) / 2 + 2.5 in
girl = (mother + father) / 2 − 2.5 in
Metric values still apply ±2.5 inches after converting to inches (not ±7.6 cm), then round to a whole centimetre.
Height converter
cm = feet × 30.48 + inches × 2.54
feet = floor(cm / 30.48)
leftover inches = cm / 2.54 − feet × 12
Height prediction is not exact. Bone-age X-rays (for example Greulich–Pyle) are more precise when a clinician needs them. CDC growth charts are the usual way to see whether a child is tracking consistently over time.
Typical adult-height methods
| Method | What it uses | Best for |
|---|---|---|
| Khamis–Roche | Age, sex, current height and weight, both parents | Ages 4–17.5 without an X-ray |
| Mid-parental (Tanner) | Parents' heights only | Unborn children and infants |
| Bone age | Hand/wrist X-ray plus current height | Clinical growth evaluation |
| Double height at 2 | Height at age 2 (boys) or 18 months (girls) | A very rough rule of thumb |
Examples
Boy, 5.2 years, 3 ft 8 in (US default)
A 5-year-old boy at 3 ft 8 in and 40 lb, with a 5 ft 5 in mother and 5 ft 10 in father, interpolates the age-5 and age-5.5 Khamis–Roche knots. Expected adult height is 5 ft 10.6 in (about 179 cm).
Same child in metric
At 112 cm and 18 kg, with parents 164 cm and 178 cm, the same method gives 181 cm. The centimetre figure differs slightly from 3 ft 8 in because 112 cm is not exactly 44 inches.
Parents only, 5 ft 2 in and 5 ft 10 in
The parents' average is 5 ft 6 in. A boy is 2.5 in above that (5 ft 8.5 in); a girl is 2.5 in below (5 ft 3.5 in).