The formula

Annualized growth velocity:
(later height − earlier height) ÷ days between measurements × 365.25

The result is usually expressed in centimeters per year. “Annualized” means the observed rate across the measurement interval has been scaled to a year; it does not mean the same rate will continue for a full year.

A worked example

An earlier height is 160.0 cm on February 18. A later height is 163.0 cm on August 18, 181 days later.

  1. Measured change: 163.0 − 160.0 = 3.0 cm.
  2. Daily rate: 3.0 ÷ 181 = about 0.0166 cm per day.
  3. Annualized rate: 0.0166 × 365.25 = about 6.1 cm per year.

Why exact dates matter

“Six months” can describe intervals with different numbers of days. Using exact dates removes that ambiguity and makes repeated calculations comparable.

Why the result is not an adult-height prediction

Growth speed changes with age and developmental timing. Multiplying a recent rate by the years remaining until age 18 assumes growth continues at the same pace and then stops on a fixed birthday. That is not a defensible basic prediction method.

Before you interpret the number

  • Check that both measurements used the same unit.
  • Use the same standing-height technique and approximate time of day.
  • Avoid short intervals that magnify measurement error.
  • Look at a series of accurate measurements rather than one pair alone.
  • Ask a clinician to interpret a concerning pattern.

Sources