Height Calculator

Step 1: Gather Required Information

Before using the calculator, you will need to know the heights of both biological parents. If you only have one parent's height available, the calculation will be less accurate, though some calculators can provide an estimate using just one parent's height with a larger margin of error. Ensure you have the most accurate measurements possible, preferably taken recently by a healthcare professional or using a proper measuring technique.

You will also need to know the child's current age and, for the most accurate results, their current height if they are old enough to stand and be measured accurately. Some versions of this calculator can provide estimates for younger children or even unborn babies using only parental heights, though these early predictions have wider margins of error.

Step 2: Select Units of Measurement

The calculator offers options for both metric (centimeters) and imperial (inches) units. Choose the system you are most comfortable with or that matches the format of the heights you have available. Most healthcare settings in the United States use inches, while most other countries use centimeters for height measurements.

Step 3: Enter Parent Heights

Enter the father's height in the appropriate field and the mother's height in the corresponding field. Ensure you enter the correct height for each parent, as swapping them will affect the calculation, particularly since the formula includes a sex-specific adjustment factor.

Step 4: Select Child's Sex

Choose whether the child is male or female from the available options. This selection is crucial because the formula applies different adjustment factors for boys and girls, reflecting the known differences in growth patterns between sexes. The adjustment accounts for the average height difference between adult men and women.

Step 5: Calculate and Review Results

After entering all required information, click the Calculate button to view the predicted adult height. The results will typically show a single predicted height in your chosen unit system, along with a range that represents the typical variation expected around that prediction.

Example Calculation

Consider a family where the father is 180 cm (5'11") tall and the mother is 165 cm (5'5") tall. They have a son.

Using the mid-parental height formula for boys: Predicted Height = (Father Height + Mother Height + 13) / 2. Predicted Height = (180 + 165 + 13) / 2 = 358 / 2 = 179 cm.

This translates to approximately 5'10.5" for the son's predicted adult height. The typical range would extend approximately 10 cm (4 inches) in either direction, so the actual adult height would likely fall between 169 cm and 189 cm.

For their daughter, the calculation would be: Predicted Height = (180 + 165 - 13) / 2 = 332 / 2 = 166 cm, or approximately 5'5.5".

Tips for Accurate Height Measurement

For the most reliable prediction, measure both parents' heights rather than relying on self-reported values. Self-reported heights tend to be overestimated by 1 to 2 cm on average, with men more likely than women to overstate their height. If possible, use a stadiometer, which is the standard medical device for measuring height. At home, you can achieve accurate measurements by having the person stand barefoot against a wall with their heels together, looking straight ahead, and marking the top of their head on the wall before measuring from the floor.

Take measurements at the same time of day for consistency. Spinal discs compress throughout the day due to gravity and activity, causing people to be 0.5 to 1.5 cm shorter in the evening than in the morning. For the most accurate results, measure in the morning soon after waking. For children, it is best to measure height at regular intervals and use the average of several measurements rather than relying on a single reading.

Mid-Parental Height Formula

The calculator uses the standard mid-parental height formula, which calculates the average of both parents' heights and applies a sex-specific adjustment:

The constant value of 13 represents the average height difference between adult men and women in centimeters (approximately 5 inches).

Converting to Imperial Units

When using inches, the formula remains the same but the constant adjusts:

• For boys: add 5 inches to the average of both parents
• For girls: subtract 5 inches from the average of both parents

Height Conversion Between Metric and Imperial

Converting heights between metric and imperial systems is straightforward using standard conversion factors. One inch equals exactly 2.54 centimeters, so to convert inches to centimeters, multiply by 2.54. To convert centimeters to inches, divide by 2.54.

For example, a height of 5 feet 9 inches is equivalent to 69 total inches (5 × 12 + 9), which converts to 69 × 2.54 = 175.26 cm. Conversely, a height of 170 cm converts to 170 / 2.54 ≈ 66.93 inches, which is 5 feet 6.93 inches. The calculator performs these conversions automatically when you switch between unit systems.

When estimating adult height, it is important to use consistent units for both parents. Mixing metric and imperial measurements will produce incorrect results unless proper conversion is applied first. The calculator handles this automatically by converting all inputs to a common unit before applying the formula.

Height Prediction Range

The calculated predicted height represents the midpoint of a statistically likely range. The standard margin of error is typically calculated as plus or minus 10 centimeters (approximately 4 inches) for either sex. This means the actual adult height is statistically likely to fall within this range in approximately 68% of cases, with wider or narrower ranges possible depending on individual factors.

Using Single Parent Height

If only one parent's height is available, some versions of the formula can estimate potential height using a modified calculation. In these cases, the adjustment is approximately twice as large, and the margin of error increases significantly because only half the genetic contribution is being accounted for in the calculation.

Factors Affecting Height

Height is a polygenic trait influenced by hundreds of genetic variants, each contributing a small effect. Studies of identical twins raised apart show that genetic factors account for approximately 80% of the variation in height within a population, while environmental factors account for the remaining 20%.

This means that while genetics set a potential range, the environment determines where within that range a child ultimately lands.

Nutrition is the most significant environmental factor. Adequate intake of protein, calcium, vitamin D, zinc, and other micronutrients is essential for normal growth. Children who experience chronic malnutrition or specific deficiencies typically achieve shorter adult heights than their genetic potential would predict. This is why average heights have increased substantially in many countries over the past century as nutrition has improved.

Hormones play a central role in regulating growth. Growth hormone, produced by the pituitary gland, stimulates the liver to produce insulin-like growth factor 1 (IGF-1), which promotes bone elongation. Thyroid hormones are also essential for normal growth, and hypothyroidism in children can significantly slow growth velocity. Sex hormones, particularly estrogen, drive the pubertal growth spurt and ultimately signal the fusion of growth plates, ending linear growth.

Sleep is an often overlooked factor. The majority of growth hormone secretion occurs during deep sleep stages, particularly during the first few hours after falling asleep. Children who do not get adequate sleep or have sleep disorders may experience reduced growth hormone secretion, potentially affecting their growth trajectory. The National Sleep Foundation recommends 9 to 11 hours of sleep per night for school-age children and 8 to 10 hours for teenagers.

Average Height Differences by Sex

Growth Percentile Classifications

Age Ranges for Growth Assessment

Understanding Growth Charts and Percentiles

Growth charts are standardized tools used by pediatricians worldwide to track a child's physical development over time [who]. The most commonly used charts are published by the World Health Organization (WHO) for children under 2 years and the Centers for Disease Control and Prevention (CDC) for children aged 2 and older [cdc]. These charts display height-for-age percentiles, allowing healthcare providers to compare an individual child's measurements against a large reference population.

A child whose height falls at the 50th percentile is exactly average for their age and sex. Those above the 95th percentile are considered tall, while those below the 5th percentile are considered short. However, the percentile alone is less important than the growth trajectory. A child who consistently tracks along the 25th percentile is growing normally, while a child who drops from the 50th to the 10th percentile over a year may require medical evaluation.

Growth charts are particularly valuable for identifying growth disorders early. Children whose height velocity slows significantly or who fall below the 5th percentile may need evaluation for growth hormone deficiency, hypothyroidism, or other medical conditions. Conversely, children who accelerate rapidly upward across percentiles may need assessment for precocious puberty or other endocrine disorders.

Key Growth Milestones

Human growth follows a predictable pattern from birth through adulthood. The most rapid growth occurs during infancy, when babies typically grow about 25 cm (10 inches) in their first year and 12 cm (5 inches) in their second year. Growth then slows to a steady rate of about 5 to 6 cm (2 to 2.5 inches) per year during the preschool and school-age years.

Puberty triggers the adolescent growth spurt, the second most rapid growth phase after infancy. In girls, this typically begins between ages 10 and 14 and peaks around age 12, with a total gain of about 20 to 25 cm (8 to 10 inches). In boys, the growth spurt begins later, typically between ages 12 and 16, peaks around age 14, and results in a total gain of about 25 to 30 cm (10 to 12 inches). Boys tend to grow for two additional years after girls stop, which partly explains the average adult height difference between sexes.

Growth ceases when the epiphyseal plates (growth plates) at the ends of long bones fuse under the influence of estrogen, which occurs in both sexes. In girls, this typically happens around ages 14 to 16 and in boys around ages 16 to 18. After fusion, no further lengthening of the long bones is possible, although spinal growth may continue slightly into the early twenties.