The size of the photo is in inches, 1 inch = 2.54cm.. The size of a seven-inch photo is 17.8cm× 12.7cm, because its standard size is 7×5 inches, and one inch is about 2.54cm. We can get this result through calculation. Compared with articles in daily life, a 7-inch photo is equivalent to the size of half a piece of A4 paper, and the size of A4 paper is 2 1cm×29.7cm, which is close to that of A4 paper.

It should be explained here that the size of a photo is usually calculated in inches, which is 2.54 cm according to the international calculation standard 1 inch, and is calculated in inches of the longer side of the photo. The commonly used photo sizes in our life are one inch and two inches, and their sizes are 2.5×3.5 cm and 3.5×4.9 cm respectively.

Basic knowledge of photo parameters

Usually, the specifications of photos are expressed in inches, which is different from the diagonal length of products such as monitors. The "several inches" in photos refers to the inch length of the long side of photos. For example, a 6-inch photo means a 6×4-inch photo. There is also a common method to express the size of a photo in the world, that is, take the integer value of the short side of the photo and add the letter R to express it. For example, a 6-inch photo has a specification of 6×4 inches, that is, 4R.

In addition, regardless of the number of pixels in a digital film, just look at the number of pixels on the long side, 1200 is 5 inches, 1400 is 6 inches, 1700 is 7 inches, and so on: 1 inch (refers to inches) =2.54cm. When we say x-inch, we mean the long side of the photo. For example, 5 inches means the photo is 2.54x5= 12.7cm, 12 inch means 2.54x 12=30.5cm, and 8x 12 means the long side is 2.54x12.

3R refers to paper, 3R is 89MM, 5R is 127MM, usually 3R refers to 3*5, which means 5 inches, and 5R refers to 5*7, which means 7 inches. R means Rectangle (English is rectangle), which is calculated by the shortest side.