How do I calculate how tall my child will be?

Use the mid-parental height. For a boy add 13 cm (5 in) to the mother's height, add the father's height and divide by 2. For a girl subtract 13 cm (5 in) from the father's height, add the mother's height and divide by 2. Example: father 180 cm, mother 165 cm, boy = (180 + 165 + 13) ÷ 2 = 179 cm.

How accurate is the mid-parental height?

It is a broad genetic target. About 95% of children reach an adult height within ±8.5 cm (about 3.3 in) of it; the American Academy of Pediatrics uses ±10 cm, two standard deviations of 5.1 cm. Nutrition, chronic illness and the timing of puberty all shift final height, and children of very tall or very short parents tend to regress toward the population average.

Is it true that a child's height at age 2 doubles?

It is a rule of thumb: doubling a boy's height at 2 years or a girl's at 18 months gives a rough adult estimate. Toddler length is measured lying down and growth before age 2 still reflects pregnancy and early nutrition, so the rule can miss by several centimeters. Use it alongside, not instead of, the mid-parental target.

What is the Khamis-Roche method?

Khamis-Roche (1994) predicts adult height from a child's current height, weight, age and the mid-parental height, using age-specific regression coefficients for children aged 4 to 17.5 years. It is usually more precise than the parental average alone once a child is school age. This page does not implement it because we could not verify the full coefficient table against the original publication.

Does this replace a doctor's assessment?

No. This is not medical advice. Growth disorders, hormonal conditions or nutritional problems can affect height regardless of parental genetics. If a child crosses percentile lines on the growth chart or is far from the target range, talk to a pediatrician or pediatric endocrinologist, who may also use a bone-age X-ray.

Can I enter heights in centimeters?

Yes. Use the unit toggle at the top of the form to switch between feet and inches and centimeters. All calculations are done in centimeters internally.

Child Adult Height Predictor

Boys: (father + mother + 13 cm) ÷ 2. Girls: (father + mother − 13 cm) ÷ 2. About 95% of children end up within ±8.5 cm (±3.3 in) of this target. Not medical advice.

Not medical advice. A population estimate for curiosity and conversation with your pediatrician, not a diagnosis.

Units

Father's height

Mother's height

Child's sex

Range

Child's height at age 2 (optional)

For the doubling rule of thumb: boys at 24 months, girls at 18 months.

Enter both parents' heights, select the child's sex, and click Predict Adult Height.

Mid-Parental Target Height Chart

Target adult height for a son / daughter, rounded to the nearest half inch. Boys = (father + mother + 13 cm) ÷ 2; girls = (father + mother − 13 cm) ÷ 2. Add ±3.3 in for the likely range.

Father ↓ / Mother →	5′1″	5′3″	5′5″	5′7″	5′9″
5′7″	5′6.5″ / 5′1.5″	5′7.5″ / 5′2.5″	5′8.5″ / 5′3.5″	5′9.5″ / 5′4.5″	5′10.5″ / 5′5.5″
5′9″	5′7.5″ / 5′2.5″	5′8.5″ / 5′3.5″	5′9.5″ / 5′4.5″	5′10.5″ / 5′5.5″	5′11.5″ / 5′6.5″
5′11″	5′8.5″ / 5′3.5″	5′9.5″ / 5′4.5″	5′10.5″ / 5′5.5″	5′11.5″ / 5′6.5″	6′0.5″ / 5′7.5″
6′1″	5′9.5″ / 5′4.5″	5′10.5″ / 5′5.5″	5′11.5″ / 5′6.5″	6′0.5″ / 5′7.5″	6′1.5″ / 5′8.5″
6′3″	5′10.5″ / 5′5.5″	5′11.5″ / 5′6.5″	6′0.5″ / 5′7.5″	6′1.5″ / 5′8.5″	6′2.5″ / 5′9.5″

Sources: the ±8.5 cm range follows the MSD Manual height-potential calculator; the ±10 cm range is the American Academy of Pediatrics version (1 SD ≈ 5.1 cm, 2 SD ≈ 10 cm). Not medical advice.

Summary

This tool estimates a child's genetic target adult height with the mid-parental height method: the average of both parents' heights plus 6.5 cm for boys or minus 6.5 cm for girls, with a ±8.5 cm range (about 95% of children) or the AAP's ±10 cm. It can also check the "double the height at age 2" rule of thumb. The result is not guaranteed because nutrition, health and puberty timing also influence final height, and it is not medical advice.

How it works

Enter the biological father's and mother's heights in feet and inches or in centimeters.
Select the child's sex. Boys get +6.5 cm (half of the 13 cm average adult sex difference), girls −6.5 cm.
Mid-parental height = (father + mother ± 13 cm) ÷ 2. This is the genetic target height.
Choose the range: ±8.5 cm covers about 95% of children (Tanner), the AAP uses ±10 cm (2 SD of 5.1 cm), and ±5 cm is roughly 1 SD.
Optionally enter the child's height at age 2 (boys) or 18 months (girls) to compare with the doubling rule of thumb.
The result is a population estimate, not a clinical growth assessment or medical advice.

Use cases

Getting a ballpark adult height estimate from both parents' heights.
Understanding how parental height influences a child's growth potential.
Comparing the genetic target with a child's own growth curve before a checkup.
Discussing growth questions with a pediatrician using quantitative context.
Helping a child understand their projected height in a fun, educational way.

Frequently Asked Questions

Last updated: 2026-10-10 · Reviewed by Nham Vu

Child Adult Height Predictor

Mid-Parental Height

Likely Target Range

Doubling Rule of Thumb

Mid-Parental Target Height Chart

Summary

How it works

Use cases

Frequently Asked Questions

Child Adult Height Predictor

Use the Child Adult Height Predictor

Mid-Parental Height

Likely Target Range

Doubling Rule of Thumb

Mid-Parental Target Height Chart

Summary

How it works

Use cases

Frequently Asked Questions