Height Calculator - Child Height Predictor | How Tall Will I Be? (2023)

Use this height calculator to predict how tall a child will be when they become an adult. Calculate the expected adult height for yourself, if you are under 18 years old (answer the ever interesting "How Tall Will I Be?" question), or for a child or teenager about whom you know the current age and stature. The height predictor supports feet and inches, as well as meters and centimeters.

Quick navigation:

  1. Using the height calculator
  2. How do we predict a child's adult height?
  3. How accurate is this height predictor?
  4. Other methods for predicting a child's adult stature
  5. Factors affecting height prospects of children
  6. Average height of United States citizens

Using the height calculator

With the help of our height calculator you can predict the future height of a child patient, your own child, or yourself, if you are still under 18. All you need as input is the current age, gender, and current height. Unlike other mature height calculators, ours does not require you to enter your weight, or your parent's heights and is just as accurate if not more accurate (see below).

So, to estimate how tall a child will be, first, select their biological sex (gender). Then enter their current age: type in whole years manually and select the number of months by rounding to the nearest whole month. For a newborn, enter zeroes in both years and months. Enter their height in feet and inches or in cm or meters. If doing this for your child or a child patient, enter their age and height. Finally, press "Predict Adult Height" to get the estimated adult height in centimeters and feet and inches from the height predictor.

The calculator works great when used to predict the height of a teenager as well.

How do we predict a child's adult height?

In this child height calculator we adopt an advanced method based on multiplier tables developed in 2004 by J.Paley et al. [1] that was developed using data published by the United States Centers for Disease Control and Prevention (CDC). The accuracy of the multiplier method was compared with the CDC growth charts (a preferred method when available) using longitudinal growth data from 52 normal children. No significant differences were noted between predictions made using the CDC growth charts versus the multiplier method meaning our tool is a highly accurate height calculator for teenagers and children alike.

(Video) Calculate How Tall You Will Be In The Future

The future prediction method was also compared to other growth databases from around the world and from different eras and the height multipliers were shown to be independent of height percentile, race, and generation, indicating that the multiplier method is universal. The accuracy of the method used in this height predictor is comparable with that of the Bayley-Pinneau [2], RWT [3], and TW3 [4] methods.

The last part is especially relevant in the U.S. and Europe where the ethnic diversity of the general population makes it impossible for pediatricians to keep up with the multitude of growth charts needed for their racially diverse patients. Furthermore, it is unclear which growth chart would be most appropriate for a multi-ethnic/multi-racial child whereas our calculator works in all circumstances.

How accurate is this height predictor?

As with any other statistical method applied to an individual the one used in our adult height predictor is prone to some error. Absolute error of prediction (AEP) is defined as the magnitude of either overprediction or underprediction of height.

For boys, the median AEP using the multiplier method ranges from 1.4 to 4.3 cm, with the error being between 1.4 and 2.7 cm for all ages except 14 years, for which the greatest errors in prediction occurred. The 90% error range is from 1.8 to 8.3 cm, with error peaks at 6 and 14 years of age and greatest accuracy at age 8 years. Regardless of age, 58% of all height predictions were within 2.5 cm (1 in), 85% of all predictions were within 5 cm (2 in), and 96% of all predictions were within 7.5 cm (3 in) of adult height for boys.

For girls, the median absolute error of height prediction calculation using the multiplier method ranges from 0.68 to 4.38 cm until age 12 years, with increasing accuracy after that. The 90% AEP ranged from 1.5 to 10.6 cm, varying from 8 to 10.6 cm until age 13 years, and increasing in accuracy after that. Disregarding age, 50% of predictions were within 2.5 cm (1 in), 68.5% of predictions were within 5 cm (2 in), and 84% of predictions were within 7.5 cm (3 in) of adult height for girls.

We recommend that the adult height calculator is used only for children without pathologic conditions that alter the potential for growth in stature and to always consult a pediatrician when making health-related decisions.

(Video) How to Predict How Tall Your Child Is Going To Be | Dr. Mandell

Other methods for predicting a child's adult stature

A number of methods for height prediction relying on examinations of skeletal structure are often used by pediatricians, for example the Bayley-Pinneau [2], the Roche-Wainer-Thissen RWT [3] and the Tanner-Whitehouse 3 method [4]. However, all these methods are subject to a wide range of error, at least partly because of the use of bone age estimations. Determination of skeletal age is relatively subjective, with a high interobserver error rate, and the relationship of skeletal age to chronologic age has been shown to differ among various ethnic groups [1]. While methods for automated bone age determination were proposed in recent years, they still require a visit to the doctor, unlike the multiplicator method.

Most online height calculators tend to use the Khamis-Roche prediction equations [5] or estimations based on the height of the mid-parent. The Khamis-Roche method has slightly larger errors than those for the Roche-Wainer-Thissen method and it requires more data than our approach using multipliers. Furthermore, the applicability of the Khamis-Roche method is limited to white American children only [5], making it unsuitable for a height predictor intended for wider application.

The mid-parent height method suffers from an issue wherein if parents are unusually tall or short, their children would be relatively less tall or short, respectively, and the mid-parental height is then a poor predictor of attained height [6] and would thus provide a poor answer to the question many adolescent boys and girls ask themselves: how tall will i grow up to be?

Factors affecting height prospects of children

The single most significant factor affecting the adult height of a child is its genetics. However, a child may not reach its full genetically-determined height potential due to other factors at play, such as:

  • Nutrition. Inadequate nutrition, both in terms of total calories consumed and in terms of making sure all macro and micro nutrients are present in the diet, can certainly hinder growth. See our daily calories calculator.
  • Hormones. Issues with hormone levels, especially growth hormone or thyroid hormones can impact the end height in both directions.
  • Diseases. Health issues, for example coeliac disease or early arthritis play a negative role
  • Genetic conditions. Some specific genetic conditions such as Marfan's syndrome or Down's syndrome have an effect on growth.

As noted, this calculator works best for healthy children without conditions with a pronounced effect on growth. GIGAcalculator.com is not a replacement for your doctor and each child is different. Make sure to consult a pediatrician to properly and fully assess your child's health condition and specific needs relative to their predicted adult height.

Good nutrition being a widely shared strong predictor is the reason why worldwide average height levels for adults have increased significantly following the Industrial revolution. The excess wealth created by more capitalist government systems and a capitalist economy enabled most children born since to receive regular food supply resulting in far less malnutrition and much higher average height for both adult men and adult women. Unless substantial changes to this economic situation such as a famine occur at a local or global level, height levels should stabilize. The method used by our height calculator should produce accurate results even in such extreme situations, as noted above.

(Video) How To Predict Height || How Tall Will You Be When You Grow Up?

Average height of United States citizens

Below we present average heights for males and females in different ages based on the US CDC growth charts with data gathered as a part of the U.S. NCHS National Health and Nutrition Examination Survey (2011-2014) [7].

Height Calculator - Child Height Predictor | How Tall Will I Be? (1)

Above is the average (mean) height comparison for U.S. citizens aged 0+, while below is the median height of U.S. citizens aged 0-20, again by gender.

Height Calculator - Child Height Predictor | How Tall Will I Be? (2)

The significant differences in adult height between the genders are an illustration on why it is such an important component of any kind of height prediction formula employed by a height predictor. Notably, the differences in future height prediction begin to increase in the early teenage years. Teenagers are also the ones often wondering "how tall will I be" for non-medical reasons.


[1] Paley J. et al. (2004) "The multiplier method for prediction of adult height.", Journal of Pediatric Orthopedics. Vol.6:732-7.

[2] Bayley N., Pinneau S.R. (1952) "Tables for predicting adult height from skeletal age: revised for use with the Greulich-Pyle hand standards" Journal of Pediatrics Vol.40:423–441

[3] Roche A.F., Wainer H., Thissen D. (1975) "The RWT method for the prediction of adult stature", Pediatrics Vol.56:1027–1033.

[4] Tanner J.M., Whitehouse R.H., Marshall W.A. et al. (1975) "Prediction of adult height from height, bone age, and occurrence of menarche, at ages 4 to 16 with allowance for midparent height", Archives of Disease in Childhood Vol.50:14–26.

[5] Khamis H.J., Roche A.F. (1994) "Predicting adult stature without using skeletal age: the Khamis-Roche method" Pediatrics Vol.4(1):504-7

[6] Wright C., Cheetham T. (1999) "The strengths and limitations of parental heights as a predictor of attained height", Archives of Disease in Childhood Vol.81(3):257–260.

(Video) How Tall Will You Be When You Grow Up?

[7] US NCHS (2016) "National Health and Nutrition Examination Survey (2011-2014)" DHHS Publication No. 1604, s.3, N 39

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