“How tall will my child be?” is one of the first questions parents ask about growth, and the oldest answer is still among the best: look at the parents. Height is strongly inherited, and the average of the two parents’ heights, adjusted for the child’s sex, predicts adult height better than most home methods. This calculator uses that mid-parental method, shows the range in which most children land, and places the result on the CDC adult stature chart so you can see how it compares with the population.
It is a statistical estimate. Many children will land outside the range, and a prediction cannot replace a doctor’s assessment if you are worried about growth.
How to use the child height predictor
- Choose the child’s sex. The adjustment is added for a boy and subtracted for a girl.
- Enter the father’s and the mother’s heights in any units, preferably measured rather than remembered.
- Read the prediction and the range. The range is the prediction plus or minus 8.5 cm (3.3 in).
- Use the percentile to see where that height sits among US 20-year-olds.
Mid-parental height formula
Girl: (father’s height + mother’s height − 13 cm) ÷ 2
Likely range: prediction ± 8.5 cm (about ± 3.3 in)
The 13 cm term is the average height difference between adult men and women, so it converts parents’ heights to a single “same-sex” equivalent. The method is the standard “target height” described by Tanner JM, Goldstein H and Whitehouse RH (Arch Dis Child 1970;45:755–762). The ± 8.5 cm band is the conventional target range used in paediatric endocrinology. The percentile uses the CDC 2000 stature-for-age LMS parameters at 20 years (Kuczmarski et al., CDC Vital Health Stat 2002;11(246)).
Worked example
Father 180 cm, mother 165 cm.
- Boy: (180 + 165 + 13) ÷ 2 = 179.0 cm (70.5 in). Range 170.5 to 187.5 cm. This is about the 62th percentile for men at 20.
- Girl: (180 + 165 − 13) ÷ 2 = 166.0 cm (65.4 in), about the 66th percentile for women at 20.
Predicted adult heights for sample parents
| Father / mother | Predicted adult height, boy | Predicted adult height, girl |
|---|---|---|
| 165 cm / 155 cm | 166.5 cm (65.6 in) | 153.5 cm (60.4 in) |
| 170 cm / 160 cm | 171.5 cm (67.5 in) | 158.5 cm (62.4 in) |
| 175 cm / 165 cm | 176.5 cm (69.5 in) | 163.5 cm (64.4 in) |
| 180 cm / 170 cm | 181.5 cm (71.5 in) | 168.5 cm (66.3 in) |
| 185 cm / 175 cm | 186.5 cm (73.4 in) | 173.5 cm (68.3 in) |
Why a child can end up outside the range
- Regression to the mean. Children of very tall or very short parents tend to be somewhat closer to the average than their parents.
- Puberty timing. Children who mature early are taller for a while but stop growing earlier; late maturers catch up.
- Nutrition and health. Chronic illness or poor nutrition in childhood can lower adult height.
- Population differences. Average heights differ between countries and generations, and the 13 cm term is an average.
Checking growth now
A prediction says where a child is likely to end up; growth charts say how they are doing today. For babies use the Baby Growth Percentile Calculator; for older children use the Child Height Percentile Calculator. The Height Converter (ft/in ↔ cm) converts between feet, inches and centimetres, and you can check body proportions with the BMI Calculator for adults.
This page is for information only and is not medical advice. If you have a heart condition, take medicines that affect heart rate, or are new to exercise, check with a doctor before starting a training plan.
Sources
- Tanner JM, Goldstein H, Whitehouse RH. Standards for children’s height at ages 2–9 years allowing for heights of parents. Arch Dis Child 1970;45:755–762.
- Kuczmarski RJ, et al. 2000 CDC Growth Charts for the United States: Methods and development. Vital Health Stat 11(246), 2002.
- Centers for Disease Control and Prevention. Stature-for-age LMS parameters, ages 2–20 years.
Frequently asked questions
How does the mid-parental height method work?
It averages the parents’ heights and adds 6.5 cm for a boy or subtracts 6.5 cm for a girl. The 13 cm gap is the average difference in adult height between men and women. The method was described by Tanner, Goldstein and Whitehouse in 1970.
How accurate is the prediction?
Roughly 95 percent of children end up within about 8.5 cm (3.3 inches) of the prediction, which is a wide range. Nutrition, health, the timing of puberty and chance all matter. The estimate is a target based on genetics, not a promise.
Can I predict height from a toddler’s height instead?
Doubling a child’s height at age 2 is a popular rule of thumb, but it is a crude one and accuracy varies. A clinician can use bone-age X-rays and growth charts for a better prediction when a growth concern exists.
Does the CDC percentile mean anything for my child?
It places the predicted height among US adults at 20 years in the CDC 2000 growth charts. A predicted height at the 50th percentile means about half of adults of that sex are taller. It tells you where the child would be expected to sit, not how they are growing now.
When should I talk to a doctor about my child’s height?
If your child is growing much more slowly than expected, has fallen across percentile lines on their growth chart, or is very far from their parents’ percentiles, ask a paediatrician. Early evaluation can find treatable causes.