In this era, the world needs solutions to improve the health and hence the immunity of working people. Over the past few years, several kinds of research occurred that deals with human-centric lighting (HCL) design which can entrain the circadian rhythm of people. This paper investigates various circadian light metrics and hence to perform a choice making for a user to select a tunable LED for HCL design. Here the capability of a selected tunable LED lamp source to complement an interior space is quantified to provide the best visual comfort and to entrain occupant circadian rhythm. Along with the Spectral Power Distribution(SPD) of the luminaire, evaluated the Correlated Color Temperature(CCT), the Color Rendering Index(CRI), the Fidelity index(Rf) and the Gamut Area Index(Rg) to establish the colour quality of the source. Here considered Melanopic-Photopic (M/P) ratio, Circadian Stimulus, and Equivalent Melanopic Lux (EML) for relating the circadian entrainment. Finally, this study aims to propose a methodology for analyzing and customizing the individual spaces for HCL design with tunable LED fixtures.