How to estimate a child's future height & weight

Written by carolyn enright
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How to estimate a child's future height & weight
Estimating your child's future height and weight makes good health sense. (children in garden image by Marzanna Syncerz from

Children hear it all of the time: "You're growing up so fast. Pretty soon you'll be as tall as your father!" It's fun trying to predict whether Jimmy will be tall and lanky like his uncle Ray or take after the shorter, stouter relatives on his mother's side. But estimating your child's future height and weight is more than simply interesting fodder for family gatherings; it can help you keep your child on track for a healthy future.

Skill level:

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Things you need

  • Tape measure
  • Digital scale

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  1. 1

    Estimate your child's future height using one of two formulas.

    How to estimate a child's future height & weight
    Measure your child's height to the nearest 1/8 inch. (tape measure image by Joann Cooper from
  2. 2

    Follow the first formula by adding the mother's height and the father's height in inches or centimetres. Add five inches (13 centimetres) for boys. Subtract five inches (13 centimetres) for girls. Divide this number by two to get an estimate of your child's future height accurate to within four inches (10 centimetres).

  3. 3

    Use the second formula to estimate your child's adult height by doubling her height at the age of two. This method is less accurate than the first.

  1. 1

    Calculate your child's Body Mass Index (BMI). There is no accurate method for predicting your child's adult weight as so many factors in addition to genetics, such as exercise and eating habits, influence weight. However, calculating a child's BMI, which indicates body fatness for most children and teens, can help you predict if your child is prone to obesity as an adult.

    How to estimate a child's future height & weight
    A digital scale is more accurate than a spring-loaded scale. Reference 3 (diet scale image by sparkia from
  2. 2

    Use a digital scale to weigh your child to the nearest decimal fraction in pounds (e.g., 18.4 Kilogram). Divide that number by 2.2 to get your child's weight in kilograms. (Example: 40.5/2.2 = 18.41.)

  3. 3

    Measure your child's height in inches (e.g., 45 inches). Multiply that number by .0254 to get his height in meters. (Example: 45 x .0254 = 1.14.) Multiply the height in meters by itself to get the height squared. (1.14 x 1.14 = 1.30)

  4. 4

    Divide the weight in kilograms by the height in meters squared. The resulting number is your child's BMI. (Example: 18.41/1.30 = 14.16)

  5. 5

    Check your child's BMI against the BMI-for-age growth charts available on the Centers for Disease Control website at If your child's BMI falls within the 5th and 85th percentiles, she is at a healthy weight for her age. If her BMI lies between the 85th and 95th percentile, she is overweight. A child with a BMI above the 95th percentile is considered obese and at high risk for type 2 diabetes.

  6. 6

    Discuss BMI results with your paediatrician. He will be able to track BMI results over time to determine if your child may be at risk for becoming overweight as an adult.

Tips and warnings

  • Keep in mind that height predictors are only estimates. Your child's height is determined by a combination of genetics and gender (70 per cent) and environmental factors, such as nutrition, exercise and health issues (30 per cent).
  • If you have your child's height and weight measurements from a recent visit to the paediatrician, use those to estimate BMI.
  • You can easily find BMI and height predictor calculators by searching for them online.
  • Avoid comparing children's height and weight. Keep in mind that children grow at different rates. Some hit their growth phase early; others are late bloomers.

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