What the Khamis–Roche estimate adds
The age-based equation combines current standing height, current weight, and the mean of the two parent heights with a sex- and age-specific regression row. Decimal age is matched to the nearest published half-year row. The published equation operates in inches and pounds, so metric entries are converted before calculation and only the displayed result is rounded.
This calculator uses the coefficient tables corrected by the 1995 Pediatrics erratum, not the misplaced decimal points from the original weight column. The source study was developed from healthy white U.S. children without growth-altering conditions. It does not use a radiograph or bone age and should not be generalized into a diagnosis for an individual child.
What the midparental estimate actually averages
For the calculator's male equation, add the mother's and father's measured heights, add 5 inches, and divide by 2. For the female equation, subtract 5 inches from the parental sum before dividing. In metric form the adjustment is 12.7 centimeters, because the international inch is exactly 2.54 centimeters. The two unit modes therefore describe one equation rather than two approximations.
Suppose the parents measure 64 and 72 inches. Their plain average is 68 inches; the male branch returns 70.5 inches and the female branch returns 65.5 inches. Those results are family reference points. Mayo Clinic calls this type of method a guess and emphasizes that there is no certain way to know an individual child's final adult height.
Measure every input on a reliable scale
Input quality matters more than adding extra decimal places to the output.
- Use current standing heights
Measure the child and both parents without shoes on firm flooring, with an upright posture and a level head. A rigid headpiece against a flat wall is preferable to guessing from a doorframe mark.
- Record a current child weight
Use a current weight measured on a suitable scale. Keep height and weight in the unit mode shown in the form; the calculator performs the exact internal conversion needed by the published regression.
- Preserve the underlying values
Average the full measurements and round only at display. Rounding each parent height first can shift a result that is already only an estimate.
Separate a family midpoint from a child's current curve
Two growth questions need different evidence.
Where might adult height center?
Khamis–Roche uses a child's current measurements as well as the family mean. The parents-only calculation supplies a rougher genetic-family anchor when no reliable child measurement is available.
Where is the child today?
The Height and Weight Percentile Calculator compares a measured visit with CDC sex- and age-specific reference data. It does not predict final height either.
How does weight relate to height during growth?
The Child and Teen BMI Calculator adds BMI-for-age screening. A height estimate cannot be repurposed as a target weight or nutrition plan.
Genes shape the frame while development changes the timetable
NIH's MedlinePlus Genetics explains that height is a complex trait influenced by many genetic variants as well as environmental factors. Neither regression can encode which variants a child inherited. They also omit gestational history, chronic disease, medication effects, nutrition, skeletal age, and the onset and pace of puberty.
Children can reach growth phases at different times, so a shorter child and a taller peer at one visit may not preserve that difference into adulthood. Clinicians look at serial measurements, family pattern, development, and health history. A surprising online estimate neither diagnoses a growth disorder nor rules one out.
Know when the prediction question has changed
An online estimate stops being the right tool when the task becomes clinical or concerns an adult.
- For a person who has reached adulthood and wants a weight-relative-to-height screen, switch to the Adult BMI Calculator instead of treating predicted stature as measured stature.
- Ask a pediatric professional about a falling growth trajectory, unusually rapid change, delayed or early puberty, persistent symptoms, or a marked mismatch with family pattern. A single equation cannot identify the reason.
- Save the estimate as a range-setting conversation aid, not a promise for clothing size, sports selection, medical treatment, or any intervention intended to alter height.