Many countries today have rapidly aging populations, and so it becomes increasingly important that standards developers design consumer products that address the accessibility needs of older persons as well as persons with disabilities. The Japanese Standards Association is presently forming several exploratory committees to address the standardization of accessible design. In 2000, Japan enacted a standard (Japanese Industrial Standard, JIS S 0011) regulating the perceptual sizes of tactile dots and bars for use in consumer products. However, these regulations were not based on highly reliable data. Therefore, objective and quantitative data for perceptual sizes of tactile dots and bars is required for revising this JIS and for devising other standards. In this study, we examine the objectively appropriate perceptual sizes for tactile dots and bars. We determine the optimal size for the tactile dot on a cellular-phone button and the optimal relative size and shape that enable a tactile dot and bar to be distinguished from one another.