Background: Advances in mobile based software application made the estimation of one’s reaction time (RT) with more accuracy and reliable. But whether the same can be established by the Ruler Drop Method (RDM) in children are not yet explored. Objective: To establish the validity of RDM in typically developing children (TDC). Method: Eighteen TDC were recruited for the cross-sectional study by the simple random sampling from recognized school. All the anthropometric measurement were taken prior to commencement of the study. In RDM, the child were made to sit with their dominant forearm resting on a flat horizontal table surface, with their open hand at the edge of the surface. When the examiner suspend and release the ruler vertically the child were instructed to catch it as quickly as possible. The distance the ruler fell was recorded, in centimetres, by measuring from the end of the ruler to superior aspect of the child’s hand. This distance was converted to reaction time in milliseconds (ms). Spearman’a Rank-Order correlation was used to establish the validity with the mobile based software application (MBSA) in estimating RT as the criterion referenced. Result: RDM shows moderate to good degree of relationship with MBSA with Spearman’s Á (rho) = 0.54 (p=0.031). Conclusion: RDM is proved to be valid among TDC. 

Keywords: Boys; Children; Girls; Reaction Time Ruler; Ruler; Ruler Drop Test; Validity.