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Child Height Predictor (Adult Height Calculator)

Predict a child's future adult height using the validated Mid-Parental (Tanner) and Khamis-Roche pediatric growth methods.

Quick Answer:Adult height is primarily determined by genetics. The Mid-Parental method adds 5 inches (13 cm) to the mother's height for boys or subtracts 5 inches from the father's height for girls, then averages the parental heights.

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How to Use the Child Height Predictor (Khamis-Roche & Mid-Parental Method)

1Select the child's sex (boy or girl).
2Enter the biological mother's height in feet/inches or centimeters.
3Enter the biological father's height in feet/inches or centimeters.
4Optionally enter the child's current age and height for advanced Khamis-Roche prediction.
5Review the projected adult height range and growth velocity insights.

Formula & How It Works

Mid-Parental (Tanner) Algorithm

Boy = (H_dad + H_mom + 13 cm) / 2 | Girl = (H_dad - 13 cm + H_mom) / 2

For boys: (Father's Height + Mother's Height + 5 inches / 13 cm) / 2. For girls: (Father's Height - 5 inches / 13 cm + Mother's Height) / 2. The 95% confidence interval is ± 2.0 to 3.5 inches.

Worked Examples

Projecting Height for a Boy

Input: Father: 6 ft 0 in (182.9 cm), Mother: 5 ft 5 in (165.1 cm)

Explanation: (182.9 + 165.1 + 13) / 2 = 180.5 cm, translating to approximately 5 ft 11 in to 6 ft 0 in.

Result: Projected Adult Height: 5 ft 11.5 in (181.5 cm) ± 3 in

Projecting Height for a Girl

Input: Father: 5 ft 10 in (177.8 cm), Mother: 5 ft 4 in (162.6 cm)

Explanation: (177.8 - 13 + 162.6) / 2 = 163.7 cm, predicting an adult stature around 5 ft 4.5 in.

Result: Projected Adult Height: 5 ft 4.5 in (163.7 cm) ± 3 in

Tall Parental Stature

Input: Father: 6 ft 4 in (193 cm), Mother: 5 ft 10 in (178 cm), Boy

Explanation: (193 + 178 + 13) / 2 = 192.0 cm, forecasting top-percentile adult height.

Result: Projected Adult Height: 6 ft 3.5 in (192.0 cm) ± 3 in

Frequently Asked Questions

How accurate is this child height predictor?▼

About 80% to 90% of children fall within ± 2 inches of their Mid-Parental height. Genetic factors account for roughly 60% to 80% of final adult stature, while the remainder is influenced by nutrition, sleep, hormones, and overall health.

What is the 'two years times two' rule?▼

A common pediatric rule of thumb suggests that doubling a boy's height at age 2, or doubling a girl's height at age 18 months, provides a rough estimate of adult height. However, Mid-Parental and Khamis-Roche methods have significantly stronger clinical backing.

At what age do girls and boys stop growing?▼

Girls typically complete the majority of their linear height growth around ages 14 to 16 (approximately 2 years after menarche). Boys usually continue linear skeletal growth until ages 16 to 18, with some continuing to age 20.

Can diet or exercise increase a child's adult height?▼

While diet cannot exceed a child's genetic potential, chronic malnutrition, vitamin D deficiency, or severe chronic stress can prevent a child from achieving their full genetic height.

When should I see a pediatric endocrinologist?▼

If a child drops multiple percentile curves on their pediatric growth chart, grows fewer than 2 inches (5 cm) per year between age 4 and puberty, or develops secondary sexual characteristics unusually early or late.

Is my personal child health data private?▼

Yes, 100%. All calculations are processed locally inside your web browser. No children's ages, heights, or parental details are ever stored or transmitted.

Quick Reference & Conversion Table

Father's Height	Mother's Height	Boy Projected	Girl Projected	Expected Range
5 ft 8 in	5 ft 2 in	5 ft 7.5 in	5 ft 2.5 in	± 3.0 inches
5 ft 10 in	5 ft 4 in	5 ft 9.5 in	5 ft 4.5 in	± 3.0 inches
6 ft 0 in	5 ft 6 in	6 ft 0.5 in	5 ft 5.5 in	± 3.0 inches
6 ft 2 in	5 ft 8 in	6 ft 2.5 in	5 ft 7.5 in	± 3.0 inches
6 ft 4 in	5 ft 10 in	6 ft 4.5 in	5 ft 9.5 in	± 3.0 inches

⚠️ Common Pitfalls to Avoid

•Treating the predicted height as an absolute guarantee rather than a statistical bell curve with ± 2 to 3.5 inches of variance.
•Using non-biological parental heights (adopted or step-parents) in genetic formula calculations.
•Failing to account for chronic pediatric medical conditions, endocrinological delays, or nutritional deficiencies.

💡 Practical Real-World Uses

•Benchmarking healthy pediatric growth percentiles alongside CDC and WHO charts.
•Identifying growth deceleration or growth plate anomalies early for pediatric endocrinology review.
•Planning long-term pediatric athletics and sports conditioning programs.

Mid-Parental Method vs Khamis-Roche Method

Feature	Mid-Parental (Tanner)	Khamis-Roche Protocol
Required Inputs	Parental heights and child biological sex	Parental heights, child current age, height, and weight
Accuracy Level	± 3.0 to 3.5 inches range	± 2.0 to 2.5 inches (higher clinical accuracy)
Applicable Ages	Birth through maturity	Children aged 4 to 17 without skeletal dysplasias
Skeletal Age Need	Does not require bone age X-rays	Does not require bone age X-rays (unlike Bayley-Pinneau)