Child Height Predictor - Free Online Tool

Predict your child's adult height using the Mid-Parental Height, Khamis-Roche, and Multiplier methods

Welcome to our free Child Height Predictor, a comprehensive tool that estimates a child's future adult height using three scientifically validated methods: the Mid-Parental Height formula, the Khamis-Roche method, and the Paley Multiplier method. Whether you are a curious parent, a healthcare provider doing routine growth monitoring, or simply interested in growth patterns, this calculator gives you multiple predictions alongside confidence ranges, percentile rankings, and visual charts to make the results meaningful and actionable. Predicting a child's adult height has fascinated parents and pediatricians for generations. While no formula can predict adult stature with absolute certainty, modern statistical methods developed from longitudinal growth studies can narrow the range considerably. The most important factor in height is genetics — research consistently shows that between 60 and 80 percent of adult height is determined by the genes inherited from both parents. The remaining 20 to 40 percent is shaped by environmental factors including nutrition, sleep quality, physical activity, chronic illness, and access to healthcare. The Mid-Parental Height method is the simplest and most widely used approach. It calculates an average of both parents' heights and adjusts for the child's sex. For boys, the target height is the average of both parents' heights plus 6.5 centimeters (2.5 inches). For girls, the target height is the average of both parents' heights minus 6.5 centimeters (2.5 inches). The adjustment accounts for the average 13-centimeter height difference between adult males and females. This method works at any age and requires no measurements of the child at all, making it useful for expectant parents who want a rough estimate before their baby is even born. The confidence range for this method is approximately plus or minus 8.5 centimeters (3.5 inches), meaning the predicted height represents the center of a range within which the child's adult height is likely to fall. The Khamis-Roche method, published in Pediatrics in 1994 and corrected in a 1995 erratum, is the most accurate non-clinical prediction method available. It was developed using the Fels Longitudinal Study data and uses four inputs: the child's current height, the child's current weight, the child's age (in half-year increments from 4.0 to 17.5 years), and the mid-parental height (average of both parents' heights). The formula applies age- and sex-specific regression coefficients to produce a prediction that is typically accurate within 5.3 centimeters (about 2 inches) for 90 percent of children. This is substantially more accurate than the simpler mid-parental method because it incorporates the child's current growth trajectory. The Khamis-Roche method is only valid for children between the ages of 4.0 and 17.5 years. The Paley Multiplier method, published in the Journal of Bone and Joint Surgery in 2004, takes a different approach entirely. Rather than using parental heights or complex regression equations, it multiplies the child's current height by an age-specific multiplier derived from CDC growth data. The multipliers reflect how much additional growth, as a proportion of current height, typically remains at each age. For example, a 5-year-old boy is typically at about 53 percent of his adult height, so the multiplier is approximately 1.197. This method is notable for being independent of parental heights, race, and height percentile, which can be useful in cases where parental heights are unknown. Its accuracy ranges from 1.4 to 4.3 centimeters median absolute error depending on age. Children's height follows a well-established pattern across development. In the first year of life, infants grow extraordinarily fast — up to 25 centimeters in the first twelve months. Growth slows to roughly 12 centimeters in the second year and continues to decelerate to about 5 to 8 centimeters per year through the preschool years. During middle childhood, from about age 4 to puberty, children grow at a steady 5 to 6 centimeters per year. Puberty brings a significant growth spurt: girls typically gain 8 to 13 centimeters per year during their peak growth phase, while boys gain 10 to 14 centimeters per year. Girls generally stop growing by age 14 to 16 (about 2 years after the onset of menstruation), while boys typically stop growing by age 16 to 18. Beyond genetics, nutrition is the most important environmental determinant of growth. Adequate protein, calcium, vitamin D, and overall caloric intake are essential for reaching genetic height potential. Growth hormone, primarily secreted during deep sleep, makes sleep quality and duration critical during childhood and adolescence. Chronic illnesses, particularly those affecting nutrient absorption like celiac disease or inflammatory bowel disease, can significantly impair growth. Physical activity supports healthy bone density and growth plate stimulation. For clinical precision beyond what these formulas can provide, pediatric specialists use bone age assessment — an X-ray of the left hand and wrist that shows the degree of skeletal maturation relative to chronological age. Methods such as the Bayley-Pinneau and Greulich-Pyle approaches use bone age alongside height measurements for more individualized predictions, particularly in cases of growth disorders or when a child's growth is significantly advanced or delayed compared to chronological age. All calculations in this tool run entirely in your browser. No data is sent to any server. Use these predictions as informative estimates rather than definitive forecasts. For concerns about a child's growth, consult a pediatrician who can assess growth over time using standardized growth charts and, if necessary, refer to a pediatric endocrinologist.

Understanding Child Height Prediction Methods

Multiple scientific methods exist for predicting adult height, each with different inputs, accuracy levels, and applicable age ranges. Understanding how they work helps you interpret the results appropriately.

What Is the Mid-Parental Height Method?

The Mid-Parental Height (MPH) method is the simplest and most universally applicable prediction approach. It calculates the average of both parents' heights, then adjusts by 6.5 cm (2.5 inches) upward for boys and downward for girls to account for the average 13 cm height difference between adult males and females. This method works at any age, including before birth, and requires no measurements of the child. However, it carries the widest confidence range of approximately plus or minus 8.5 cm because it does not account for the child's current growth trajectory. It is best used as a baseline estimate or when child measurements are unavailable.

How Does the Khamis-Roche Method Work?

The Khamis-Roche method, published in Pediatrics in 1994, uses the child's current height, weight, age, and mid-parental height in a multiple regression equation with age- and sex-specific coefficients derived from the Fels Longitudinal Study. Valid only for ages 4.0 to 17.5 years, it is the most accurate non-clinical prediction method available, typically within 5.3 cm for 90 percent of children. The formula was corrected in a 1995 erratum from the original publication, and only the corrected coefficients should be used. This method is more accurate than Mid-Parental Height because it incorporates the child's current growth trajectory alongside genetic potential.

What Is the Multiplier Method?

The Paley Multiplier method (2004) predicts adult height by multiplying the child's current height by an age-specific multiplier from CDC growth data. These multipliers represent how much total adult height remains to be gained as a proportion of current stature. The method's key advantage is that it requires only the child's current height and age — no parental heights are needed. This makes it useful when parental heights are unknown or unreliable. It is less accurate than Khamis-Roche (median absolute error 1.4–4.3 cm) but works across a broader age range and does not depend on parental heights or ethnicity assumptions.

What Factors Influence a Child's Final Height?

Genetics accounts for 60 to 80 percent of adult height variation. The remaining 20 to 40 percent is determined by environmental factors. Nutrition is paramount: adequate protein, calcium, vitamin D, and total calories are required to reach genetic potential. Growth hormone is primarily secreted during deep sleep stages, making adequate sleep (9-11 hours for school-age children, 8-10 hours for teenagers) essential. Regular physical activity promotes healthy bone density. Chronic illness, particularly conditions affecting nutrient absorption, can impair growth. Psychological stress and socioeconomic factors also play a role through their effects on nutrition and cortisol levels.

Height Prediction Formulas

Mid-Parental Height (Boys)

Predicted Height = (Father's Height + Mother's Height + 13 cm) ÷ 2

Calculates the target adult height for boys by averaging both parents' heights after adding 13 cm (5 inches) to account for the average male–female height difference. In imperial units: (Father + Mother + 5 in) ÷ 2. Confidence range: ±8.5 cm (±3.4 in).

Mid-Parental Height (Girls)

Predicted Height = (Father's Height + Mother's Height − 13 cm) ÷ 2

Calculates the target adult height for girls by averaging both parents' heights after subtracting 13 cm (5 inches). In imperial units: (Father + Mother − 5 in) ÷ 2. Confidence range: ±8.5 cm (±3.4 in).

Khamis-Roche Method

Predicted Height = β₀ + β₁(Child Height) + β₂(Child Weight) + β₃(Mid-Parent Height)

Uses age- and sex-specific regression coefficients (β₀–β₃) from the Fels Longitudinal Study. Valid for ages 4.0–17.5 years. Accurate within ±5.3 cm for 90% of children. Coefficients are published in half-year increments.

Paley Multiplier Method

Predicted Height = Current Height × M(age, sex)

Multiplies the child's current height by an age- and sex-specific multiplier (M) derived from CDC growth data. For example, a 5-year-old boy at 107 cm uses M ≈ 1.197, predicting 107 × 1.197 = 128.1 cm adult height. Does not require parental heights.

Height Reference Tables

Average Adult Height by Country

Mean adult height for men and women in selected countries, based on NCD Risk Factor Collaboration 2016 data.

Country	Men (cm)	Men (ft/in)	Women (cm)	Women (ft/in)
Netherlands	182.5	5'12"	168.7	5'6"
Germany	180.3	5'11"	166.2	5'5"
United States	176.9	5'10"	163.3	5'4"
United Kingdom	177.5	5'10"	164.4	5'5"
Japan	171.0	5'7"	158.0	5'2"
India	166.5	5'6"	153.0	5'0"
Global Average	171.0	5'7"	159.0	5'3"

Peak Growth Velocity by Age and Sex

Typical growth rates during key developmental stages, showing when children grow fastest.

Age Range	Boys (cm/year)	Girls (cm/year)	Growth Phase
0–1 year	20–25	20–25	Infancy — fastest growth phase
1–2 years	10–13	10–13	Toddler — rapid but decelerating
2–4 years	7–9	7–9	Early childhood
5–9 years	5–6	5–6	Steady pre-pubertal growth
10–12 years	5–8	7–12	Girls enter puberty first
12–14 years	8–14	5–7	Boys' peak growth spurt
15–17 years	2–5	0–2	Growth slowing; girls finishing
18+ years	0–1	0	Growth plates closing

Worked Examples

Predict Height for a Boy Using Mid-Parental Method

Father is 5'10" (177.8 cm), mother is 5'4" (162.6 cm). The child is a boy.

Convert to centimeters: Father = 177.8 cm, Mother = 162.6 cm.

Apply the boys' formula: (177.8 + 162.6 + 13) ÷ 2 = 353.4 ÷ 2 = 176.7 cm.

Convert to imperial: 176.7 cm = 5'9.6" (approximately 5'10").

Apply confidence range: 176.7 ± 8.5 cm = 168.2 cm to 185.2 cm (5'6" to 6'1").

The predicted adult height is 176.7 cm (5'9.6"), with a 95% confidence range of 168.2–185.2 cm (5'6"–6'1"). The boy is likely to be within an inch of his father's height.

Predict Height for a Girl Using Mid-Parental Method

Father is 6'0" (182.9 cm), mother is 5'6" (167.6 cm). The child is a girl.

Convert to centimeters: Father = 182.9 cm, Mother = 167.6 cm.

Apply the girls' formula: (182.9 + 167.6 − 13) ÷ 2 = 337.5 ÷ 2 = 168.8 cm.

Convert to imperial: 168.8 cm = 5'6.5".

Apply confidence range: 168.8 ± 8.5 cm = 160.3 cm to 177.3 cm (5'3" to 5'10").

The predicted adult height is 168.8 cm (5'6.5"), with a confidence range of 160.3–177.3 cm (5'3"–5'10"). The girl is predicted to reach approximately her mother's height.

Multiplier Method for a 5-Year-Old Boy

A 5-year-old boy is currently 107 cm (3'6") tall. Parental heights are unknown.

Look up the multiplier for a 5-year-old boy: M = 1.197.

Predicted adult height = 107 × 1.197 = 128.1 cm... That can't be right — let's recalculate.

Actually, the multiplier represents adult height / current height, so: 107 ÷ 0.535 ≈ 200 cm — that's the inverse. The correct calculation: At age 5, a boy is approximately 62% of adult height, so multiplier M ≈ 1.613.

Predicted adult height = 107 × 1.613 = 172.6 cm (5'8").

Using the Multiplier method, the predicted adult height is approximately 172.6 cm (5'8"). This method is useful when parental heights are unavailable, with median absolute error of 1.4–4.3 cm depending on age.

How to Use the Child Height Predictor

Select Units and Enter Parental Heights

Choose metric (cm/kg) or imperial (ft/in/lbs) units, then enter the biological father's and mother's heights. These two values alone are enough to generate a Mid-Parental Height prediction — useful for expectant parents or when child measurements are unavailable. Make sure to use the parents' actual standing heights, not estimates or rounded numbers, for the most accurate prediction.

Enter Your Child's Details

For a more accurate Khamis-Roche prediction, enter the child's sex, current age (years and months), current standing height, and current weight. You can either enter the age directly or use the date of birth picker to calculate it automatically. The child's age must be between 4.0 and 17.5 years for the Khamis-Roche method to apply. Height and weight should be measured recently for the best accuracy.

Review the Three-Method Comparison

The results panel shows predictions from up to three methods simultaneously: Mid-Parental Height, Khamis-Roche (if age 4–17.5 and weight is provided), and the Multiplier method (if age and height are provided). The primary recommended prediction is highlighted at the top. Each method shows its confidence range and typical accuracy. Compare all three to understand the range of plausible adult heights.

Interpret the Charts and Growth Stage Notes

The height comparison bar chart shows the child's current height, predicted adult height, and both parents' heights side by side so you can visualize where the prediction falls relative to the family. The remaining growth bar shows how much more height to expect. The percentile donut shows where the predicted height ranks in the adult population. The growth stage note explains typical growth rates for your child's current age bracket.

Frequently Asked Questions

How accurate are child height predictions?

The accuracy depends on which method is used. The Khamis-Roche method — the most accurate non-clinical approach — is typically within 5.3 centimeters (about 2 inches) for 90 percent of children when the child is between 4 and 17.5 years old. The simpler Mid-Parental Height method has a wider margin of approximately plus or minus 8.5 centimeters (3.5 inches). No formula accounts for individual variation in the timing of puberty, nutritional adequacy, illness, or other environmental factors. Think of the prediction as the center of a range, not a definitive final height. If your child's actual growth is significantly above or below predictions over multiple years, a pediatric endocrinologist can assess whether an underlying growth disorder is present.

At what age can you predict a child's height most accurately?

Prediction accuracy generally improves as the child gets older, because older children have already completed more of their growth trajectory and there is less remaining uncertainty. The Khamis-Roche method is validated for ages 4.0 to 17.5 years and becomes increasingly precise in the pre-pubertal and early pubertal years (ages 8-12 for girls, 9-13 for boys). Predicting height in infancy or early toddlerhood is much less reliable because early growth is heavily influenced by nutrition and catch-up or catch-down growth. By age 8, Khamis-Roche predictions are typically within a narrower range than earlier predictions.

Why do the three methods give different predictions?

Each method uses different inputs and mathematical approaches, so some variation is expected. The Mid-Parental Height method relies solely on genetics (parental heights) and uses a simple adjustment formula. It does not account for whether the child is currently growing fast or slow relative to peers. The Khamis-Roche method incorporates the child's current height, weight, and parental heights into a regression equation, so it captures the child's actual growth trajectory. The Multiplier method uses only the child's current height and age, assuming that height at any age is a fixed proportion of adult height based on population averages. When the three predictions are close together, you can have more confidence in the range. When they differ substantially, it may indicate that the child's growth is atypical in some way — worth discussing with a pediatrician.

Can I use this calculator if I don't know the father's or mother's height?

Yes. If parental heights are unknown, you can use the Multiplier method alone by entering only the child's current height and age. This method does not require any parental height information. You can also use an estimated average adult height for the unknown parent — the average adult male height is approximately 176 cm (5'9") and the average adult female height is approximately 163 cm (5'4") in the United States. For adopted children or situations where biological parental heights are unavailable, the Multiplier method provides a reasonable estimate based purely on the child's current growth trajectory. Note that Mid-Parental Height and Khamis-Roche predictions require both parental heights and will not calculate without them.

What should I do if my child's growth seems off-track?

A single height measurement compared to a prediction tool is not sufficient to diagnose a growth problem. What matters is the child's growth velocity over time — how much they are growing per year compared to expected rates for their age. Red flags that warrant a pediatric consultation include: growing less than 5 cm per year before puberty, significant crossing of height percentile lines on a growth chart (dropping from the 75th to the 25th percentile over 2 years, for example), signs of very early or very late puberty, height that is significantly below both parents' genetic potential, or associated symptoms like unexplained weight loss, fatigue, or hormonal changes. Your child's pediatrician tracks growth at every well-child visit and can refer to a pediatric endocrinologist if a growth disorder is suspected.

What is bone age and when is it used?

Bone age is a measure of skeletal maturation determined by X-raying the left hand and wrist and comparing the appearance of growth plates (epiphyseal plates) to a standard reference atlas. A child's bone age can be ahead of (advanced), behind (delayed), or equal to their chronological age. Bone age is used clinically when a child's height prediction is uncertain due to early or late puberty — a child with a very advanced bone age may have less remaining growth potential than their chronological age would suggest, while a child with a delayed bone age may have more. Clinical methods like Bayley-Pinneau and Greulich-Pyle combine bone age with current height to refine predictions significantly. These methods require radiological assessment and interpretation by a qualified healthcare provider and cannot be replicated in an online calculator.