A lot of folks get confused about how to measure the visual size of photos and other images that are created or viewed on their computers.
The simplest way is by counting how many pixels (tiny dots) were used to make that image. A thumbnail-size photo, like those in your Friends List on Facebook, might only be 50 pixels wide by 50 pixels high. The video you watch on YouTube might be 560 x 315 pixels. A photo that fills the entire screen on your laptop might be something like 1280 x 800.
The mental trap to avoid is measuring the images on our screens using inches or centimeters. We’re all looking at different devices, whether it’s a phone in our hand, a tablet on our lap, or a computer on our desk. Different screens fit more or fewer pixels into each inch on that screen. Therefore, an image the size of a postage stamp on my laptop screen, might be the size of a wallet photo when displayed on your older computer monitor, but the size of fingernail on your smartphone.
In a world where we view most images on a screen, there are no inches, there are only pixels — until you print the picture.
