Refraction predictions from intraocular lens (IOL) calculation formulae are inaccurate in children. We sought to quantify the relationship between age and prediction error using a model derived from the biometry measurements of children enrolled in the Infant Aphakia Treatment Study (IATS) when they were ≤7 months of age. We calculated theoretical predicted refractions in diopters (D) using axial length, average keratometry, and IOL powers at each measurement time point using the Holladay 1 formula. We compared the predicted refraction to the actual refraction and calculated the absolute prediction error (APE). We found that the median APE was 1.60 D (IQR, 0.73-3.11 D) at a mean age (corrected for estimated gestational age) of 0.20 ± 0.14 years and decreased to 1.11 D (IQR, 0.42-2.20 D) at 10.60 ± 0.27 years. We analyzed the association of age with APE using linear mixed-effects models adjusting for axial length, average keratometry, and IOL power and found that as age doubled, APE decreased by 0.25 D (95% CI, 0.09-0.40 D). The accuracy of IOL calculations increases with age, independent of biometry measurements and IOL power.