Child Height Predictor Calculator
Predict child adult height from parents with honest range.
What it does
Parent heights sketch the likely adult height. Tall parents tend toward tall kids, short toward short, with a few inches of swing either way.
The tool above averages the parents into a midparent, then shifts for sex. A 70 in father and 65 in mother give 67.5 in midparent, so a boy predicts 70 in, or 5 ft 10 in, inside 68 to 72 in. The metric match is 178 cm inside 173 to 183 cm.
The 2.5 in shift reflects average sex differences in growth. Girls subtract where boys add, which keeps brothers and sisters on separate but parallel tracks.
Ranges carry the honesty. Most kids land within 2 in of the line, while early or late puberty, nutrition, sleep, and chronic illness move individuals.
Growth charts still rule childhood. A child drifting across percentiles needs a pediatrician and maybe a bone age, not parent math alone.
How to use
- Pick imperial (in) or metric (cm).
- Enter father height: 70 in or 178 cm suits the default.
- Enter mother height.
- Pick boy or girl.
- Read predicted height first.
- Read range and midparent next.
Formula
- dad
- Father standing height.
- mom
- Mother standing height.
- sex
- Boy adds, girl subtracts.
Metric uses plus or minus 6.5 cm around the midparent average. Half of kids land inside the band; timing of puberty shifts the rest.
Worked example
Example: 70 and 65 in parents, boy
Imperial defaults: 70 in father, 65 in mother, boy. These are also the default values, so the page opens on this answer.
- Father: 70 in. Mother: 65 in.
- Midparent: (70 + 65) / 2 = 67.5 in.
- Boy adjust: 67.5 + 2.5 = 70 in.
- Feet: 70 in is 5 ft 10 in.
- Range: 68 to 72 in.
- Tool shows 70 in (5 ft 10 in), 68 to 72 in, 67.5 in midparent.
Reference table
| Parents | Boy | Girl |
|---|---|---|
| 68 and 63 in | 68 in | 63 in |
| 70 and 65 in | 70 in | 65 in |
| 72 and 66 in | 71.5 in | 66.5 in |
| 178 and 165 cm | 178 cm | 165 cm |
Limits
- Estimate only, not a promise.
- Puberty timing swings years of growth.
- Nutrition and illness shift results.
- Bone age beats parent math off curve.
Common mistakes
- Reading the line as exact inches.
- Mixing shoes-on heights into the average.
- Applying adult math to toddlers with worry.
- Ignoring a percentile drift.
- Comparing siblings on one line.
Try it yourself
Quick checks. Answers sit tucked under each question.
72 and 66 in parents, boy?
Midparent is (72 + 66) / 2 = 69 in. Boy is 69 + 2.5 = 71.5 in. Range is 69.5 to 73.5 in.
180 and 170 cm parents, girl?
Midparent is (180 + 170) / 2 = 175 cm. Girl is 175 - 6.5 = 168.5, shown as 169 cm. Range is 164 to 174 cm.
Questions
How tall will a boy be?
Average the parents, then add 2.5 in for boys or subtract 2.5 for girls. Here (70 + 65) / 2 + 2.5 = 70 in.
How wide is the range?
Most kids land within 2 in above or below the estimate. Here 68 to 72 in.
Metric version?
Use (father + mother) / 2 in cm, then plus or minus 6.5 cm. Here (178 + 165) / 2 + 6.5 = 178 cm.
Genes or food?
Genes set the band; food, sleep, and health decide where inside. Chronic illness and poor nutrition can cost inches.
What if growth stalls?
No. Bone age and growth charts beat parent math for teens off curve.
Does this predict weight?
No. This page estimates growth, not adult health.