Usually x inches refers to the length of the long side of the photo, in inches. For example, 1 inch means that the photo length is 2.54x1= 2.54cm; 5 inches means that the length of the photo is 2.54×5 = 12.7 cm .. The normal error should be around1~ 2 mm. If the "gap" is too large, it means that there is something wrong with the printing shop.
Extended data:
There are also some other special ID photos, although they are all one inch, but there are still some subtle differences in size. For example, the photo length and width of a generation of ID cards are 2.2cm x 3.2cm respectively; The length, width and size of the photo of the second-generation ID card are 2.6cm x 3.2cm respectively; The length and width of graduates' photos are 33 mm× 48 mm respectively; The length and width of the driver's license are 22mm×32mm respectively? ; The length and width of ordinary ID photos are 33mm*48mm respectively.
In order to ensure the photo quality and the unity of portrait size, angle, posture and color, the Ministry of Public Security has formulated and issued the Technical Standard for Digital Photographs for ID Card Making (GA46 1-2004). All photos must be recent bareheaded color headshots, with the headshots accounting for 2/3 of the photo size, white background without borders, clear images, rich layers, natural expressions and no obvious distortion.
Reference: Baidu Encyclopedia-photo size