How it works
Boy's target = (father + mother + 13 cm) ÷ 2. Girl's target = (father + mother − 13 cm) ÷ 2. Mid-parental target range = target ±8.5 cm. Rough toddler rule = measured height × 2.
- Choose a method and the child's sex.
- Enter the relevant heights in centimetres or feet and inches.
- Read the estimate with its uncertainty and growth guidance.
Worked example: For a father of 180 cm and mother of 165 cm, a boy's mid-parental target is (180 + 165 + 13) ÷ 2 = 179 cm. The target range is 170.5 to 187.5 cm. A girl's target for the same parents is 166 cm.
Example mid-parental height estimates
| Child | Predicted adult height | Height in feet and inches | Estimated target range | Parents' heights |
|---|---|---|---|---|
| Boy | 179 cm | 5 ft 10.47 in | 170.5 to 187.5 cm (5 ft 7.13 in to 6 ft 1.82 in) | 180 / 165 cm |
| Girl | 166 cm | 5 ft 5.35 in | 157.5 to 174.5 cm (5 ft 2.01 in to 5 ft 8.7 in) | 180 / 165 cm |
| Boy | 174 cm | 5 ft 8.5 in | 165.5 to 182.5 cm (5 ft 5.16 in to 5 ft 11.85 in) | 175 / 160 cm |
| Girl | 161 cm | 5 ft 3.39 in | 152.5 to 169.5 cm (5 ft 0.04 in to 5 ft 6.73 in) | 175 / 160 cm |
| Boy | 176.68 cm | 5 ft 9.56 in | 168.18 to 185.18 cm (5 ft 6.21 in to 6 ft 0.91 in) | 5 ft 10 in / 5 ft 4 in |
Swipe the table sideways to see the rest.
Targets and ranges are estimates, not individual growth assessments.
Things to consider
- Measure without shoes on a level floor.
- Use 24 months for boys and 18 months for girls in the rough rule.
- Growth patterns matter more than a single estimate.
- Speak to a doctor or child health nurse about growth concerns.
Frequently asked questions
How accurate are height predictors?
Mid-parental height is an approximate genetic target. About 95% of children fall within 8.5 cm either side of this target, but it cannot guarantee an individual's final height. Nutrition, health and puberty timing affect growth. The toddler doubling rule is less reliable and has no validated range here.
What is the mid-parental height formula?
Add the father's and mother's heights in centimetres. Add 13 cm for a boy or subtract 13 cm for a girl, then divide by 2. The target range extends 8.5 cm either side of the result.
Why does the formula use 13 cm?
The 13 cm adjustment reflects an approximate average difference between adult male and female heights. It is a population-based estimate, not a fixed difference for every family or child.
When do children stop growing?
Girls typically finish growing around 14 to 16 years and boys around 16 to 18 years. Timing varies with puberty and individual development, and some children grow later.
Does the age-2 rule work?
Doubling toddler height is only a rough rule of thumb. Use a boy's height at 24 months or a girl's height at 18 months. It does not account for later growth or puberty timing, so this calculator does not attach a target range to it.
What other height prediction methods are available?
Health professionals may use a bone age X-ray or the Khamis-Roche method alongside growth records and clinical assessment. These are not implemented here. A doctor can advise whether further assessment is appropriate.
Results are estimates for general information only, not financial, medical or professional advice.