GoGrowHow the height calculator works
This calculator uses the mid-parental height method (also called target height), first described by the paediatrician James Tanner. It's the same starting point UK doctors use when they look at a child's growth chart.
Boys: (Dad's height + Mum's height + 13 cm) ÷ 2
Girls: (Dad's height + Mum's height − 13 cm) ÷ 2
The 13 cm adjusts for the average height difference between adult men and women. The result is the middle of a range: most children finish within about 8.5 cm either side of it.
A worked example
Dad is 178 cm (5'10") and Mum is 163 cm (5'4"). For their son: (178 + 163 + 13) ÷ 2 = 177 cm, so a likely range of about 168.5 to 185.5 cm (5'6" to 6'1"). For a daughter: (178 + 163 − 13) ÷ 2 = 164 cm, a range of about 155.5 to 172.5 cm (5'1" to 5'8").
Why the range is so wide
Parents' heights only tell part of the story. Brothers and sisters with the same parents can end up 10 cm or more apart. A child's current height, where they sit on the growth chart, and when puberty starts all change where they land in the range.
That's why a sharper estimate also looks at how tall your child is now for their age. GoGrow does this using growth chart percentiles, and you can update it each time you measure.
Growth spurts: what to expect
| Girls | Boys | |
|---|---|---|
| Growth spurt usually starts | Around 10–11 | Around 12–13 |
| Fastest growth | Around 11–12 | Around 13–14 |
| Close to adult height | Around 15–16 | Around 17–18 |
These are averages. Early and late developers are both normal, and a late developer often keeps growing for longer.
Average UK child height by age
Approximate 50th centile (the middle) on UK growth charts. Half of children are taller and half are shorter.
| Age | Boys | Girls |
|---|---|---|
| 4 | 103 cm (3'5") | 102 cm (3'4") |
| 6 | 116 cm (3'10") | 115 cm (3'9") |
| 8 | 128 cm (4'2") | 127 cm (4'2") |
| 10 | 139 cm (4'7") | 138 cm (4'6") |
| 12 | 149 cm (4'11") | 151 cm (4'11") |
| 14 | 163 cm (5'4") | 160 cm (5'3") |
| 16 | 173 cm (5'8") | 163 cm (5'4") |
What helps a child reach their potential
- Sleep. Growth hormone is mostly released during deep sleep. Primary-age children generally need 9–12 hours and teenagers 8–10.
- Enough food, especially protein. Regular meals with protein, dairy or calcium-rich alternatives, fruit and vegetables.
- Moving every day. Around an hour of activity a day supports healthy bones and muscles.
- Good general health. Long-term illness can slow growth, so keep up with check-ups.
None of these will make a child taller than their genes allow. They help a child grow to their own natural potential.
Frequently asked questions
How accurate is a child height calculator?
The parent-height method puts about 95% of children within roughly 8.5 cm either side of the middle estimate. It's a guide, not a guarantee. Adding the child's current height and growth chart position narrows it down.
When do girls stop growing?
Most girls reach close to their adult height around 15 or 16, usually about two years after their first period. The fastest growth is typically between 10 and 14.
When do boys stop growing?
Most boys reach close to their adult height around 17 or 18. Their growth spurt usually comes later than girls', typically between 12 and 16.
Can sleep, food or exercise make my child taller?
Genes set most of a child's height range. Good sleep, enough food and regular activity help a child grow to their natural potential, but nothing reliably adds height beyond it.
What if one parent's height is unknown?
The method needs both. If you don't know one, the UK adult average (about 175 cm for men and 162 cm for women) gives a rough guide, but the estimate will be less reliable.
When should I see a doctor about my child's height?
See your GP or health visitor if your child seems to have stopped growing, is dropping across growth chart lines, is much shorter than family members, or if puberty starts very early or very late.
Parent guides
Sources
- Tanner JM, Goldstein H, Whitehouse RH. Standards for children's height at ages 2–9 years allowing for height of parents. Archives of Disease in Childhood, 1970.
- RCPCH: UK-WHO growth charts, 2–18 years
- CDC: Growth charts
This calculator gives an educational estimate only. It is not medical advice and can't diagnose a growth problem. If you're worried about your child's growth, speak to your GP or health visitor.