How tall will I be? Quiz
This how tall will I be quiz asks five questions: sex, age, current height, weight and your parents’ heights. It turns the answers into an adult height estimate with a published formula: Khamis-Roche if you answer everything, the mid-parental formula from your parents’ heights alone, or your CDC growth-chart percentile carried forward to age 20. Skip anything you don’t know. The result is a statistical estimate with a range, not medical advice.
The quiz
Five questions. Leave blank anything you don’t know.
Only the Khamis-Roche formula uses weight.
All math runs in your browser. Nothing you enter is uploaded or stored.
Your result
Answer the questions and press See my result. You need at least age and current height, or both parents’ heights.
How the quiz turns answers into a height
Most “how tall will I be” quizzes score answers about sleep, sport or shoe size and map the total to a height. This one does not score anything. Each answer is an input to a published formula, and the quiz uses the most informed formula your answers allow.
| What you answered | Formula used | Range shown |
|---|---|---|
| All five questions, age 4 to 17.5 | Khamis-Roche | ±5.3 cm (boys) or ±4.3 cm (girls): the 90% error bound reported in the 1994 paper |
| Both parents’ heights (with or without the rest) | Mid-parental target height | about ±8.5 cm |
| Age and current height, age 2 to 20 | CDC percentile carried to age 20 | none: we could not verify a published error range for this method |
| Anything less | No result | – |
When your answers allow more than one formula, the result shows all of them next to each other, with the headline taken from the first row that applies. If the formulas disagree by a lot, that is useful to know: it means the estimate is uncertain.
One person, three levels of answers
To show what each extra answer changes, here is the same girl run through the quiz three ways: age 12, 150 cm, 42 kg, father 179 cm, mother 165 cm.
| Questions answered | Formula | Estimated adult height | Range shown |
|---|---|---|---|
| Parents’ heights only | Mid-parental | 165.5 cm (5′5″) | 157.0 – 174.0 cm |
| Age and height only | CDC percentile (44th percentile at 12) carried to 20 | 162.3 cm (5′4″) | none available |
| All five | Khamis-Roche | 165.4 cm (5′5″) | 161.1 – 169.7 cm |
The three answers are 3.2 cm apart. None of them is “the” answer; the last one simply uses the most information and comes with the narrowest published range.
What the quiz does not ask, and why
- Shoe size, sleep, diet, sport. We could not find a published, validated formula that predicts adult height from these, so asking would only make the number look more informed than it is. Sleep, nutrition and health do matter for growth; there is just no formula here that can turn them into centimetres.
- Puberty stage. It matters a great deal, since early and late developers finish at different ages, but assessing it properly is a clinician’s job. This is the main reason the result is a range. For typical timing see when boys stop growing and when girls stop growing.
- Your name, e-mail or anything identifying. The quiz runs in your browser. Your answers are not uploaded or stored.
Limits
Khamis-Roche was built from healthy white US children in one long-running study, and one prediction in ten in that study fell outside its 90% band. The mid-parental formula ignores how the child is actually growing. Carrying a percentile forward assumes you stay on the same growth-chart line, which early and late developers do not. Our Khamis-Roche coefficients were cross-checked against two worked examples and two independent open implementations, not against every digit of the printed tables. The method comparison has more on each.
Common questions
- Is this quiz accurate?
- It is as accurate as the formula it ends up using, and it tells you which one that was. No quiz or calculator can know your adult height in advance.
- I am already 18 or older. Does it still work?
- Up to 20 it can place your height on the CDC chart and carry the percentile to 20, which at that age changes little. Khamis-Roche stops at 17.5. For how much the typical person still grows at your age, Am I done growing? is the better tool.
- Would the full calculator give a different answer?
- No. The height predictor uses the same Khamis-Roche and mid-parental code with all the fields on one screen.
Sources: Khamis HJ, Roche AF. “Predicting adult stature without using skeletal age: the Khamis-Roche method.” Pediatrics. 1994;94(4):504–507; erratum 1995;95(3):457. 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;45:755–762. Kuczmarski RJ, et al. “2000 CDC Growth Charts for the United States: methods and development.” Vital and Health Statistics 11(246), 2002; stature-for-age LMS data file from cdc.gov/growthcharts.