Understanding image DPI

When it comes to digital images, be in photography, graphic design or any other digital imagery it’s often seen that the image needs to be (let’s say) 300dpi. But what is DPI and how does it affect my images?

DPI or PPI is known as dots per inch or pixels per inch and what it’s function is sort of explained in the name of it, but it’s still something a lot of people don’t seem to understand very well.

Lets get one thing straight right now. The DPI/PPI value is practically only relevant for printing images.

If we look at this photo of a bird with the info window showing.

We can see here the physical image resolution of 4414 x 2923 pixels. This image is that size. We can also see that it is currently set to a DPI/PPI of 300.

In this software (GNU Image Manipulation Program) it indicates that with this physical resolution, printed at 300 ppi we can print to a size of 373 x 247 millimeters in size.

What happens though if our printer only prints at 180 ppi?