The total phenolic contents (TPCs) represent the bioactive substances and antioxidant capacities of flora products. The present study employed digital images from a smartphone to determine the TPCs in tea products and their liquors. Various parameters related to the portable home-made colorimetric analysis box design were optimized to achieve the most favorable capturing condition. The proposed method performance was evaluated, which agreed with the Appendix F of AOAC (2016). In comparison with the standard UV–vis, no statistical differences (t-tests, P = 95 %) were observed, and there were advantages of simplicity, portability, sample volume reduction, decreased analysis time, low-cost operation, especially the potential to be used by tea producers, managers, and consumers to quickly analyze the TPCs. The results demonstrate the descending TPCs orders of green > white > oolong > black teas (recoveries of 95–98 %) and the increase of TPCs in tea liquors regarding the rising brewing temperature and duration.