Abstract: One variation of a method includes: accessing a skin type of a user; predicting a first set of locations occupied by the user during a first future time interval; based on historical ultraviolet irradiance data and the first future time interval, calculating a first predicted unprotected ultraviolet radiation exposure of the user during the first future time interval; calculating a maximum allowable ultraviolet radiation exposure for periods within the first future time interval based on the skin type of the user; calculating a first minimum sun protection factor predicted to reduce the first predicted unprotected ultraviolet radiation exposure to less than the maximum allowable ultraviolet radiation exposure; selecting a first sunscreen formula characterized by a first sun protection factor greater than the first minimum sun protection factor; and shipping the first volume of the first sunscreen formula to the user prior to the first future time interval.