Child Height Predictor

How tall will my child be?

The calculator above does that arithmetic, and then does something the formula cannot: if your child has already been measured, it checks which growth curve they are actually on and moves the estimate toward it.

How accurate is a child height predictor?

Accurate enough to plan around, not accurate enough to bet on. From the parents alone, the honest answer is a 17 cm window — about 94% of children land somewhere inside it. That sounds wide because it is: at this point the only evidence is genetics.

Your child's own height narrows it, and age does the rest. A measurement at ten cuts the window to roughly 10 cm; by sixteen there is so little growing left that the estimate is close to what you can already see. No calculator does better than this without an X-ray of the hand, and the ones claiming a single exact number are rounding away the part that matters.

How to use this child height predictor

Put in the mother's and the father's heights and pick the child's sex. That is enough — the estimate appears straight away. If you don't know the sex yet, leave it on Not sure yet — that is where it starts — and you get both answers at once.

If your child has already been born, switch the card to My child is here and add their age and current height. That single measurement usually does more for the estimate than anything else you can tell the calculator, because it shows which growth curve the child is actually on rather than which one their genes suggest.

Everything runs in your browser. Nothing is uploaded, nothing is stored, and there is no sign-up.

How to read your result

The big number is the single most likely adult height. The bar under it is the part that matters more: the likely range. A height predictor deals in ranges, and a child who lands 5 cm either side of the estimate has not defied it — they have landed exactly where the model expected.

With parents' heights alone, that range is about ±8.5 cm, which is the 3rd-to-97th percentile of adult heights for a family like yours. Add your child's current height and it narrows, because the calculator now has evidence instead of only genetics.

The two methods behind the number

Mid-parental height

The classic pediatric formula, published by James Tanner in 1970. Take the average of the parents' heights, then add 6.5 cm for a boy or subtract 6.5 cm for a girl. It is the same arithmetic doctors do at a growth check, and its virtue is that it needs nothing but the parents — so it works before the child is born.

Percentile-channel projection

Children tend to grow along the same percentile line year after year: a toddler at the 60th percentile usually turns into a teenager near the 60th percentile. So we convert your child's height into a percentile against the CDC growth charts, hold that percentile to age 20, and read the adult height back off the curve.

The final estimate blends the two, leaning further on the child's own curve the older they are. At two, the parents carry most of the answer. At fourteen, the child's curve does.

A worked example

A 165 cm (5′5″) mother and a 178 cm (5′10″) father, run through the calculator three ways:

The daughter's measurement moves the estimate up by 3 cm and narrows the range from 17 cm to 10 cm. At 145 cm she is taller than about 85% of ten-year-old girls, and that is the information the parents' heights alone could never supply.

Average height by age

Where does your child sit today? These are the median heights from the same CDC growth charts the calculator uses — the 50th percentile, meaning half of children that age are taller and half are shorter.

Notice the crossover: girls are taller than boys at twelve, then boys overtake them for good by fourteen. Girls start puberty earlier and finish growing earlier, which is why a tall twelve-year-old girl and a tall twelve-year-old boy are not the same prediction at all.

What the calculator can't see

Height is roughly 80% genetics. The other 20% is everything a calculator has no way of knowing about:

• Nutrition — sustained protein, calcium and vitamin D through the growing years.
• Sleep — most growth hormone is released during deep sleep.
• Puberty timing — an early start means an earlier finish, and often a slightly shorter adult height than the curve implied.
• Chronic illness — celiac disease, thyroid and growth-hormone conditions all bend the curve, and most are treatable once found.
• Measurement error — shoes, hair and a wobbly toddler are worth more centimeters than people expect. Measure barefoot, heels against a wall.

When is a child's height finally set?

Growth stops when the growth plates in the long bones close, which happens roughly two years after puberty begins in earnest. For most girls that is 14 to 16; for most boys, 16 to 18. Late bloomers keep adding height into their late teens, which is exactly why a prediction made at 12 is looser than one made at 16.

For the full picture of why height runs in families and how growth charts are read, see our guide to how tall your baby will be.

When to talk to a doctor

This tool is educational, not diagnostic. If it tells you your child's growth curve is tracking well away from what their parents' heights predict, that is worth a mention at the next check-up — not because something is wrong, but because a pediatrician can tell in minutes whether it is a growth spurt, a puberty timing difference, or something worth looking into.

The same goes for a child who has crossed two percentile lines downward, stopped growing for a year, or is far outside the range you expected. A doctor with the child's full growth history sees things no calculator can.