A sizing gauge (4) is structured to be used with a patient (8) and is structured to enable an identification of a particular patient interface that is most appropriately sized for the patient. The sizing gauge includes a support portion (12) and a sizing portion (16). The sizing portion includes a first gauge element (36) and a plurality of second gauge elements (40A,40B,40C). The first gauge element is disposed on the support portion and is structured to be positioned at a first location on the patient's face. The plurality of second gauge elements are disposed on the support portion and are situated at locations spaced from the first gauge element. The distance between the first gauge element and each second gauge element is representative of a size in one direction (44) of each of at least some of the plurality of patient interfaces. At least one of the plurality of second gauge elements comprises a tactile feature.