Height Calculator
Predict how tall a child will be from the mother's and father's heights, with the likely range, try the double-at-two rule of thumb, convert height between feet and inches and centimeters, and compare two people's heights.
Height calculator: predict a child's adult height
Toddler rule of thumb
Height converter and comparison
How the height predictor works
The mid-parental height method (Tanner) is what pediatricians use for a quick genetic target: average the parents' heights, then add 2.5 inches (6.5 cm) for a boy or subtract 2.5 inches for a girl. Formally: boy = (mother + father + 5 in) ÷ 2; girl = (mother + father − 5 in) ÷ 2. About 95% of children end up within roughly 4 inches (10 cm) of this target.
Example: mother 5'4" (64 in), father 5'10" (70 in): a son's target is (64 + 70 + 5) ÷ 2 = 69.5 in (5'9.5"), likely between 5'5.5" and 6'1.5"; a daughter's is 64.5 in (5'4.5").
Other ways to estimate adult height
- Double height at 2: boys reach about half their adult height around age 2 and girls around 18 months. It's a folk rule with wide error.
- Khamis-Roche: uses the child's current height and weight plus parents' heights; more accurate for ages 4 to 17 but needs published coefficient tables by age.
- Bone age: a hand X-ray read by a doctor shows how much growth is left; it's the most accurate for children who are growing early or late.
Nutrition, sleep, chronic illness and puberty timing all shift the result. If a child is falling across percentile lines on the CDC growth charts, or is far from the family target, ask a pediatrician.
Average US adult height
CDC data (NHANES 2015–2018) put the average American man at about 5'9" (175.3 cm) and woman at about 5'3.5" (161.3 cm), age 20 and over.
Common questions
How tall will my child be?
Mid-parental estimate: average the parents' heights, then add 2.5 inches for a boy or subtract 2.5 inches for a girl. Most children land within about 4 inches of that.
How accurate is the height calculator?
The mid-parental method has about ±4 inches of error (95% range). Bone-age methods done by a doctor are more precise.
Is it true you double your height at age 2?
Roughly, for boys at 2 and girls at 18 months, but it's a rule of thumb with wide error.
What is the average height for a man in the US?
About 5'9" (175 cm) for men and 5'3.5" (161 cm) for women, per CDC NHANES 2015–2018.
How many cm is 5'9"?
175.3 cm (69 inches × 2.54).
Sources
- CDC: Growth charts
- CDC NCHS: Anthropometric reference data for children and adults, 2015–2018
- Tanner, Goldstein & Whitehouse (1970): Standards for children's height at ages 2–9 allowing for height of parents
Related
General information, not financial, tax or legal advice. Check important numbers with the official source before acting on them.