The size of the photo is in inches, 1 inch =2.54cm, and usually x inches refers to the inch length of the long side of the photo. For example, 5 inches means that the photo length is 2.54x5 =12.7cm; 12 inch means that the length of the photo is 2.54x12 = 30.5cm. ..

Note: The normal error should be around 1 ~ 2mm.

Extended data:

What is the photo size ratio? resolution ratio

5-inch photo 3X5 800X600 resolution

6-inch photo? 4X6 1024X768 resolution

7-inch photo? 5X7 1024X768 resolution

8-inch photo? 6X9 1280X960 resolution?

References:

Photo Size-Baidu Encyclopedia