Height Calculator - Child Height Predictor
Estimate how tall a child will grow as an adult. Choose the mid-parental height method for a quick two-input answer, or switch to Khamis-Roche for a more precise prediction that also factors in the child's current height, weight, and age. Results appear in both centimetres and feet/inches, with a confidence range and a comparison to the CDC median for the same age.
How height prediction works
Two validated methods are widely used to estimate a child's adult height. The mid-parental height formula is the simpler of the two: it averages the biological parents' heights and then adds 6.5 cm for a boy or subtracts 6.5 cm for a girl. The result is the genetic target height, with about 95% of children landing within 8.5 cm either side of it. Because it needs only the parents' heights, it works at any child age - even before the child is born. The Khamis-Roche method, published in Pediatrics in 1994, adds the child's current height, weight, and age to the calculation. Using multiple regression coefficients calibrated separately for boys and girls at each two-year age interval from 4 to 17, it shrinks the typical margin of error to about 5 cm (2 inches) compared with 10 cm (4 inches) for the mid-parental method. The drawback is that it was validated specifically in Caucasian American children, so it may be less accurate for other ethnic groups.
What affects how tall a child grows
Genetics accounts for approximately 60-80% of a person's adult height, which is why parental heights are the strongest predictor. The remaining 20-40% reflects environmental influences during the growing years. Adequate nutrition - particularly enough total calories, protein, calcium, and vitamin D - is the most important environmental factor. Chronic illness, certain medications (including prolonged corticosteroid use), and hormonal conditions such as growth hormone deficiency or hypothyroidism can all reduce final adult height. Sufficient sleep matters too because the majority of growth hormone is released during deep sleep. Regular physical activity supports healthy development, though very intense training during puberty can occasionally delay growth plate closure. Children who are significantly taller or shorter than this calculator predicts should be evaluated by a pediatrician.
When children stop growing
Growth continues until the growth plates - cartilaginous zones near the ends of the long bones - fuse and harden. In girls, growth plates typically fuse between ages 14 and 16, roughly two years after the onset of menstruation. In boys, fusion usually occurs between ages 16 and 19, later because puberty starts later and lasts longer. The most precise way to determine remaining growth potential is a bone-age X-ray, most commonly of the left hand and wrist evaluated against the Greulich-Pyle atlas. A pediatric endocrinologist uses bone age together with the methods above to give a narrower prediction interval than any calculator alone.
Limitations of height calculators
No formula predicts adult height with certainty. The Khamis-Roche method was developed on a specific population and has a standard deviation of about 2.5-5 cm depending on age and sex, meaning roughly one in three children will fall outside that range by at least that amount. Adoption, donor gametes, or unknown parental heights make the mid-parental method inapplicable. Health conditions, surgeries, or medications not captured by this tool can shift outcomes substantially. The calculator is intended as an informal guide, not a medical assessment.
Median height by age (CDC, 50th percentile)
| Age (years) | Boys (cm) | Boys (ft/in) | Girls (cm) | Girls (ft/in) |
|---|---|---|---|---|
| 4 | 102 | 3 ft 4 in | 101 | 3 ft 4 in |
| 6 | 115.5 | 3 ft 9 in | 115 | 3 ft 9 in |
| 8 | 128 | 4 ft 2 in | 127.5 | 4 ft 2 in |
| 10 | 138.5 | 4 ft 7 in | 138 | 4 ft 6 in |
| 12 | 149 | 4 ft 11 in | 151.5 | 4 ft 12 in |
| 14 | 163.8 | 5 ft 4 in | 160.5 | 5 ft 3 in |
| 16 | 173.5 | 5 ft 8 in | 162.5 | 5 ft 4 in |
| 18 | 176 | 5 ft 9 in | 163 | 5 ft 4 in |
| 20 | 177 | 5 ft 10 in | 163 | 5 ft 4 in |
Approximate median standing heights for boys and girls at even ages, based on CDC growth charts. Actual heights vary widely.
Frequently asked questions
How accurate is the mid-parental height formula?
The mid-parental method has a margin of error of about 4 inches (10 cm) for 95% of children. That means if the formula predicts 170 cm, the actual adult height will most likely land between 160 cm and 180 cm. It is a useful genetic target, not a guarantee. The Khamis-Roche method cuts that error roughly in half by including the child's own current measurements.
What is the Khamis-Roche method?
Developed by Dr. Harry Khamis and Dr. Alex Roche and published in Pediatrics in 1994, it estimates adult stature using a multiple regression equation that combines a child's current height, current weight, age, and the average of both parents' heights. Separate equations are used for boys and girls at each two-year age interval from 4 to 17. The typical margin of error is about 2 inches (5 cm) at 68% confidence.
At what age do boys stop growing?
Most boys reach their full adult height between ages 16 and 18, though the growth plates can remain open until age 19 in some cases. Boys start puberty later than girls on average, which is why their growth spurt comes later and they often continue growing for longer after it begins.
At what age do girls stop growing?
Girls typically stop growing around age 14 to 15, which is roughly two years after they begin menstruating. Their growth spurt usually starts between ages 8 and 13 and is more compressed than the male growth spurt. Most girls gain little additional height after their menstrual cycle is established.
Can nutrition increase a child's adult height?
Yes, within the limits set by genetics. Children who consistently meet their nutritional needs - particularly for total calories, protein, calcium, vitamin D, and iron - are more likely to reach the upper end of their genetic height potential. Chronic undernutrition during childhood is one of the leading causes of stunted growth worldwide. However, eating more than needed for healthy growth does not push height above the genetic ceiling.
Is height 80% genetic?
Studies of twins and adopted children suggest that roughly 60-80% of the variation in adult height across a population is explained by genetic differences. The remaining 20-40% reflects environmental factors, primarily nutrition and health during childhood and puberty. This means genetics sets the range, but environment determines where within that range a child ends up.
How do I measure a child's height accurately?
Have the child stand barefoot against a flat wall with feet together and heels touching the wall. The child should look straight ahead so that the line of sight is parallel to the floor. Place a flat book or ruler horizontally on top of the head touching the wall, then mark the wall at that point and measure from the floor to the mark with a tape measure. First-thing-in-the-morning measurements tend to run about 1 cm taller than evening measurements due to spinal compression during the day.