A facemask package integrated with a mask sizing ruler is disclosed. The package stores the masks of various sizes. The mask sizing ruler comprising a first measuring gauge element, a second measuring gauge element and one or more sizes indicated thereon. The sizes in the sizing ruler are determined by categorizing one or more precisely previously measured distance from at least two points on one or more human faces into one or more sizes based on at least one distance on one or more masks of one or more mask sizes. At least one distance on one or more masks of one or more mask sizes is proportional to the maximum vertical distance of the mask in unfolded state. A system and method for determining the sizes indicated on the mask ruler are also disclosed. The sizing ruler precisely indicates the size of the mask that most appropriate to a user as the sizes are categorized from real human face dimensions.
