The family calculation

The free GetTall predictor uses the traditional midparental-height method. It combines the measured heights of both biological parents with a standard sex-reference adjustment.

Male reference: (mother’s height + father’s height + 13 cm) ÷ 2
Female reference: (mother’s height + father’s height − 13 cm) ÷ 2

This produces a family-based center. GetTall then displays a deliberately broad ±10 cm reference range. The range discourages false precision and does not guarantee where adult height will land.

The current CDC reference

The second result uses exact age in months, current standing height and the selected male or female CDC stature-for-age chart. The published CDC LMS values are interpolated for the entered age and used to calculate a z-score and percentile.

This percentile describes where one measurement sits on the selected population reference today. GetTall does not project that percentile forward or present it as a predicted final adult height.

Why this is not a complete prediction

Parental height explains only part of the variation in adult height. A family formula does not evaluate the person’s current growth pattern, developmental timing, health history, skeletal maturity or the quality of a home measurement.

The 2024 analysis “Accurate Prediction of Children’s Target Height from Their Mid-Parental Height” also describes regression to the mean: children of unusually tall parents tend, on average, to be closer to the population mean than the uncorrected formula implies, and the reverse can occur for unusually short parents.

What the app may add

GetTall App is designed to add current height, dated measurement history, growth velocity, measurement quality and developmental timing context. Until the model has completed independent validation, GetTall describes this as a more personalized outlook, not a clinically validated or high-precision prediction.

Daily sleep, nutrition or movement task completion is intentionally separate from the long-term height forecast. Completing a habit does not directly move the predicted range.

Privacy boundary

The free web calculation runs locally in the browser. Age, current height, parent heights, reference choice and outputs are not submitted to GetTall, stored in a marketing database or attached to analytics. Anonymous funnel events may record that the tool was started or completed, but those events contain no height or health values.

Sources

Version history

Version 1.1 · August 2026: Added age, current height, shared imperial/metric controls and a separate CDC stature-for-age percentile.

Version 1.0 · August 2026: Initial midparental-height web method, broad ±10 cm display range and browser-only computation.