How Tall Will I Be? Free Adult Height Predictor
Every kid who has ever been the shortest or the tallest in class has asked the same question: how tall will I be when I'm done growing? There is no way to know the exact number in advance — but there is a well-established way to get close. This page explains the method behind the calculator above, what really decides your adult height, and when growth actually stops.
How this height predictor works
The calculator blends two independent estimates instead of relying on one.
1. The mid-parental height method
This is the formula paediatricians have used for decades. It is simple arithmetic on your parents' heights:
| If you are | Formula |
|---|---|
| A boy | (father's height + mother's height) ÷ 2 + 6.5 cm |
| A girl | (father's height + mother's height) ÷ 2 − 6.5 cm |
So if dad is 178 cm and mum is 165 cm, a son's mid-parental estimate is (178 + 165) ÷ 2 + 6.5 = 178 cm, and a daughter's is 165 cm. In feet and inches that's 5'10" and 5'5". The method is deliberately blunt — it assumes you land near the middle of your family's genetic range.
2. Current-height projection
The second estimate ignores your parents entirely and looks at where you are now. At any given age, children have already completed a predictable share of their total growth. A 14-year-old boy is typically at about 91% of his final height; a 14-year-old girl at about 97%. Divide current height by that fraction and you get a projected adult height.
The calculator weights the two estimates together, which is why it asks for your age and current height rather than parents alone. Where the two disagree sharply — a short child of tall parents, or the reverse — the range widens, and that gap is itself worth mentioning to a doctor.
Expect a range, not a number. Mid-parental estimates usually land within about 5 cm (2 inches) of the real outcome. Anyone promising an exact final height is selling you something.
What actually decides how tall you'll be
Roughly 80% of your adult height is genetic. That share is fixed the day you're born and no routine changes it. The remaining slice is where daily habits matter — not because they add height beyond your genetic ceiling, but because poor habits stop you from reaching it.
- Sleep. The largest pulses of growth hormone are released during deep sleep. Teenagers running on six hours a night through their growth years are working against their own biology.
- Nutrition. Adequate protein, calcium, vitamin D and total calories. Chronic undernutrition during puberty is one of the few things that measurably lowers final height.
- Physical activity. Movement supports bone development and healthy body composition. It does not "stretch" you taller, despite what basketball folklore says.
- Health conditions. Untreated thyroid problems, growth hormone deficiency, coeliac disease and some chronic illnesses affect growth. These are worth ruling out if a child is falling off their growth curve.
Notice what is not on the list: hanging from bars, height-increase supplements, and posture devices. Once the growth plates close, none of it adds a millimetre of bone.
When do you stop growing?
Growth ends when the epiphyseal plates — the cartilage zones near the ends of long bones — harden into solid bone. The timing differs by sex by about two years:
| Growth spurt | Usually finished | |
|---|---|---|
| Girls | 10 – 14 | 14 – 16, about 2 years after first period |
| Boys | 12 – 16 | 16 – 18, sometimes into 19 – 20 |
During the peak of the spurt, boys can add 7–10 cm in a single year and girls 6–9 cm. This is also why predictions made mid-spurt are less stable than predictions made before it starts or after it ends.
Start with your situation
The calculator adapts its questions depending on who's answering. Pick the closest fit:
↑ Or run the free predictor now — it takes about 60 seconds and shows your result without an account.
Frequently asked questions
How can I tell how tall I will be?
The most reliable at-home method is the mid-parental height formula: average your parents' heights, then add 6.5 cm for a boy or subtract 6.5 cm for a girl. Combining that with your current height for your age narrows the estimate further. The calculator above does both and gives you a likely range.
At what age do you stop growing?
Most girls reach their final adult height around 14 to 16, roughly two years after their first period. Most boys finish between 16 and 18, and some keep adding a centimetre or two until 19 or 20. Growth stops when the growth plates in the long bones close.
How accurate is a height predictor?
The mid-parental method typically lands within about 5 cm (2 inches) of final adult height. It is an estimate, not a diagnosis. Accuracy drops for children who are unusually early or late in puberty, or who have a medical condition affecting growth.
Can I still get taller?
If your growth plates are still open — usually meaning you are still in or before puberty — yes, you have growing left to do. Sleep, nutrition and staying active all help you reach your genetic potential. Once the plates close, no supplement, stretch or routine adds real height.
Does it work for both girls and boys?
Yes. The calculator applies a different formula and a different growth-maturity curve for boys and girls, because girls start and finish puberty roughly two years earlier.
Do I need to sign up to see my result?
No. The predicted height and range are shown for free with no account and no email. You only enter an email if you want the full personalized growth plan.
This tool provides a statistical estimate for general information only. It is not medical advice, diagnosis or treatment. If you are concerned about a child's growth, speak to a paediatrician or family doctor.