ToolnozaUnderstand the method
Start with measured heights for both biological parents in the same unit. The calculator uses the parents’ average with a sex-specific adjustment of 5 inches, equivalent to 12.7 cm, before dividing by two. It does not need a child’s current age because this particular method estimates a parental target rather than extrapolating a growth curve.
Worked calculation
For the boy formula, add 180 + 165 + 12.7 = 357.7 cm, then divide by 2 to get 178.85 cm. For the girl formula, subtract 12.7 instead: 332.3 ÷ 2 = 166.15 cm. The adjustment applies to the sum, not to the average afterward.
Practical checks
Convert a result by dividing centimeters by 2.54 to get total inches. Divide by 12 to get complete feet and retain the remaining inches. Do not write 5 feet 8 inches as 5.8 feet: inches use twelfths of a foot. The length converter can check a conversion independently.
Use the free tool
Enter both parents’ heights, select units and the formula for a boy or girl.
Formula reference
Boy: (father + mother + 12.7 cm) / 2. Girl: (father + mother − 12.7 cm) / 2. 1 inch = 2.54 cm.
Limits
A rough estimate, not a growth assessment. Nutrition, puberty and health affect final height. Discuss growth concerns with a pediatrician.