Greulich and Pyle Bone Age Calculator
Updated October 12, 2026
What does Bone Ager show for a Greulich and Pyle bone age?
Greulich and Pyle bone age is an atlas comparison of a hand radiograph with reference standards of skeletal maturity. Bone Ager shows the Brush Foundation mean and standard deviation for the chronological age, and the model estimate stays separate from that mean. This calculator reports the interpolated Brush values. Atlas plate matching is outside this page.
Brush Mean and Standard Deviation
The numbers follow the Greulich and Pyle 1959 Brush Foundation tables, as reproduced by Gaskin, Kahn, Bertozzi, and Bunch in 2011. The lookup uses chronological age in completed months. It interpolates between published ages and stops at the ends of the table. Female ages cover 3 to 192 months. Male ages cover 3 to 204 months. Outside those ages the mean and standard deviation are unavailable.
The on-screen label is Brush Mean and SD. The page also compares the unrounded estimate with that mean plus or minus two standard deviations. Below the lower limit the label is Delayed. Above the upper limit the label is Advanced. A result on either boundary, or between them, is Within 2 SD. The band is centered on the Brush mean. The same page states that a clinician reviews any medical interpretation.
Reference films shown after an estimate come from the RSNA training set. Those films are educational examples with training labels. The measured error for the model estimate is on About.