Quick takeaway: This height calculator estimates a child's adult height from the heights of their biological parents. For a boy, add 5 inches to the parents' combined height and divide by 2. For a girl, subtract 5 inches before dividing. A father who is 5 feet 10 inches and a mother who is 5 feet 5 inches give an estimate of 5 feet 10 inches (177.8 cm) for a boy.
How Tall Will My Child Be
Enter the biological parents' heights and choose the child's sex for the formula. The adult height estimate updates immediately. Switch between centimeters and feet/inches, or choose the height comparison modes to compare figures and calculate a height difference.
The default method uses parent heights only. Age, weight, and current child height are not required. The current height field in the visual comparison mode changes the picture, not the adult height estimate.
Height Prediction Formula
This is the mid-parental height method described by Mayo Clinic.
- Boys: Adult height in inches = (Father height + Mother height + 5) / 2
- Girls: Adult height in inches = (Father height + Mother height - 5) / 2
The common metric version uses a 13 cm adjustment. This calculator applies the 5-inch formula, then converts the result using 1 inch = 2.54 cm, so changing units preserves the same estimate. Five inches equals 12.7 cm, close to the rounded 13 cm convention.
Evidence note: American Family Physician describes projected adult heights as usually lying within about 4 inches (10 cm) of mid-parental height. The displayed range is this broad family reference, not a personalized confidence interval or a guarantee.
Fully Worked Real-World Example
Suppose the biological father is 5 feet 10 inches and the biological mother is 5 feet 5 inches.
- Convert the father to inches: 5 × 12 + 10 = 70 inches.
- Convert the mother to inches: 5 × 12 + 5 = 65 inches.
- For a boy, calculate (70 + 65 + 5) / 2 = 70 inches.
- Convert to centimeters: 70 × 2.54 = 177.8 cm.
- Apply the broad ±4-inch reference: 66 to 74 inches, or 5 feet 6 inches to 6 feet 2 inches.
For a girl with the same parents, (70 + 65 - 5) / 2 = 65 inches, or 5 feet 5 inches (165.1 cm). The broad reference range is 61 to 69 inches.
How to Convert Height
For a height of 5 feet 8 inches:
Total inches = 5 × 12 + 8 = 68
Centimeters = 68 × 2.54 = 172.72 cm
To convert centimeters back, divide by 2.54 for total inches. Divide that value by 12, keep the whole number as feet, and use the remaining inches.
Common Mistakes
- Treating a prediction as a promise. Siblings can have different adult heights even though the formula gives them the same family estimate.
- Mixing up decimal feet and feet/inches. A height of 5 feet 6 inches is 5.5 feet, not 5.6 feet.
- Entering 12 in the inches box. Carry a full 12 inches into the feet box; 5 feet 12 inches becomes 6 feet 0 inches.
- Using shoes or guessed parent heights. Measure without shoes and use both biological parents' standing heights.
- Using the visualizer as a growth chart. The silhouettes compare height. They do not calculate age-based growth percentiles.
Understanding the Estimate
This tool calculates a family height estimate. It does not use bone age or assess a child's growth pattern. Mayo Clinic explains that adult height cannot be predicted with certainty and recommends discussing growth concerns with a healthcare professional.