Disposable hypodermic needles are essential tools in endodontic therapy. Their basic function is injection of irrigating solutions into the root canal for the purpose of removing debris and microorganisms from the root canal during chemomechanical preparation. The objective of this study was to determine the similarities, in gauge/size number, length and color-coding system, between disposable hypodermic needles and endodontic files/reamers. Search engines such as google.com and google scholar were used to collect data on disposable hypodermic needles and files/reamers based on diameter, gauge/size number, length and color-coding system. The obtained data were compared between the two groups of instruments with a view to finding similarities in their sizes, color-coding systems and lengths. The two groups of instruments exhibited variations in lengths, numbering and color-coding systems. However, there were striking similarities between the outer diameters of disposable needles (gauge 28-17) and the diameters of the tips of reamers/files (size 35-40) respectively. It was concluded that disposable hypodermic needles with gauge number 28-17 and files/reamers with number 35-140 are similar in their outer diameters. The understanding of the similarities between these two groups of instruments, within the specified gauge/number ranges, will assist in appropriate selection of needles for root canal irrigation as well as in the technical design of disposable hypodermic needles for carrying plastic materials in orthograde apical third root filling technique.