Background: Growth rate of nails is affected by various conditions. However, little is known about the anatomic factor which can predict the nail growth rate. Objectives: To investigate the anatomic factors that could predict the growth rate of thumbnails. Methods: Twenty-four healthy young adults were enrolled in the study. We marked a line with ultrapulse CO₂ laser on thumbnails at the baseline. Thumbnails were photographed with ruler at the baseline and six weeks after marking. The distance from the mark to the proximal nailfold, and the length of lunula and cuticle was measured by analyzing magnified photos with ImageJ. Results: The female to male ratio was 1.4:1 and the mean age was 30.3 years (24-39 years). Growth rate of dominant hand thumbnails was faster than that of non-dominant hand thumbnails (3.85 vs. 3.28 mm/ month, P < 0.0001). Cuticle length was positively correlated with thumbnail growth rate (r=0.3946 and P=0.0055), and cuticle length of dominant hand thumbnails was longer than that of non-dominant hand thumbnails (P=0.0002). Age, sex, height, weight, body mass index (BMI), length of lunula were not significantly associated with thumbnail growth rate. Conclusion: This study highlights the role of cuticle in predicting thumbnail growth rate. These results could be helpful in the treatment of nail disorders as well as for investigation on medication affecting nail growth rate.