Height
Calculator
Predict a child's adult height using mid-parental height or current age and height. Convert between cm, feet/inches, and meters instantly.
Height Growth Stages by Age
Average annual height gain by life stage.
Average Height by Age (US, CDC Data)
50th percentile heights for US boys and girls.
| Age | Boys (50th %ile) | Girls (50th %ile) | Notes |
|---|---|---|---|
| 2 years | 2 ft 10 in / 86 cm | 2 ft 9 in / 84 cm | Rapid toddler growth phase |
| 4 years | 3 ft 5 in / 104 cm | 3 ft 5 in / 103 cm | Similar heights for boys/girls |
| 6 years | 3 ft 10 in / 116 cm | 3 ft 9 in / 115 cm | Steady childhood growth |
| 8 years | 4 ft 2 in / 128 cm | 4 ft 2 in / 127 cm | Girls start puberty sooner |
| 10 years | 4 ft 6 in / 138 cm | 4 ft 7 in / 140 cm | Girls slightly taller at 10 |
| 12 years | 4 ft 11 in / 149 cm | 5 ft 1 in / 152 cm | Girls' puberty growth spurt |
| 14 years | 5 ft 4 in / 163 cm | 5 ft 3 in / 160 cm | Boys overtake girls at ~14 |
| 16 years | 5 ft 8 in / 173 cm | 5 ft 4 in / 162 cm | Most girls near adult height |
| 18 years | 5 ft 9 in / 176 cm | 5 ft 4 in / 163 cm | Boys still growing slightly |
| Adult | 5 ft 9.3 in / 175.3 cm | 5 ft 4.0 in / 162.1 cm | US national average |
Genetics Accounts for 60–80% of Adult Height
The best predictor of a child's height is their parents' heights. Environmental factors — especially nutrition during the first 1,000 days and sleep quality during puberty — can help a child reach (but not exceed) their genetic potential. No supplement, exercise, or diet can override genetic limits.
Height is a polygenic trait — controlled by hundreds of genes, not just one. Studies of identical twins show that about 60–80% of height variation between people is genetic.
The remaining 20–40% is influenced by environmental factors: nutrition (especially protein and micronutrients like zinc and vitamin D), sleep, exercise, and overall health. A child raised in optimal conditions will reach their genetic potential; poor nutrition or chronic illness can fall short of it.
About 70–80% of human growth hormone (HGH) is released during deep sleep — specifically during slow-wave (N3) sleep stages. This makes sleep duration and quality directly tied to growth in children and teenagers.
School-age children (6–13) need 9–11 hours. Teenagers need 8–10 hours. Chronic short sleep doesn't just cause tiredness — it can impair growth hormone output, potentially limiting height gains during critical growth windows.
How to Predict a Child's Adult Height
While no method can perfectly predict adult height, two scientifically validated approaches give useful estimates: the Mid-Parental Height Method and the Multiplier Method. Our calculator uses both.
Mid-Parental Height Method
This is the simplest and most widely used method. It estimates a child's genetic target height based solely on parental heights, with a margin of error of ±4 inches (±10 cm).
Multiplier Method (CDC-Based)
This method uses the child's current height and age to apply a growth multiplier derived from CDC longitudinal data. It accounts for where the child currently is in their growth trajectory and gives a more personalized prediction than the parental method alone.
How to Convert Height Between Units
Factors That Influence Height
Adult height is determined by the interplay of genetic and environmental factors across the entire growth period — from conception through the end of puberty.
Genetics (60–80%)
Height is highly heritable. Genome-wide association studies have identified over 700 genetic variants associated with height, though no single gene dominates. Children with two tall parents are likely to be tall; children with two short parents are likely to be shorter — but there is always variance. A child with a genetic potential of 5'10" won't grow to 6'2" regardless of diet or exercise.
Nutrition (Critical During Key Windows)
The first 1,000 days of life (conception through age 2) is the most critical nutritional window for growth. Stunting — permanent height deficit from early malnutrition — affects approximately 22% of children worldwide. During puberty, caloric and protein intake directly support the growth spurt. Calcium and vitamin D are essential for bone density and length.
Hormonal Factors
Growth hormone (GH), insulin-like growth factor 1 (IGF-1), thyroid hormones, and sex hormones (estrogen and testosterone) all play critical roles in regulating height. Growth hormone deficiency is a medical condition that causes short stature and can be treated with synthetic GH therapy if diagnosed early. Precocious puberty (early onset) can initially accelerate height but leads to earlier growth plate closure, resulting in shorter adult height.