Despite the importance of retirement savings, many individuals retire with lack of adequate retirement savings. While calculating retirement savings needs was found to enhance retirement savings, little is known about what underlies this enhancement. Applying the theory of planned behavior (TPB), we developed a model in which psychological factors influence the calculation of retirement savings needs, which in turn influences the ownership of individual retirement accounts. Path analysis was used to test our model with data from the 2015 National Financial Capability Study. The results showed that favorable attitudes, strong social norms, and perceived behavioral control are associated with calculating retirement savings needs. Also, calculating retirement savings needs as well as perceived behavioral control and having an employer-based retirement plan, in turn, contributed to the prediction of individual retirement account ownership. Our results suggest it is important to understand he psychological factors behind calculating retirement savings needs and to make it easy for individuals to calculate those needs.