### Rule of Thumb

We'll start off with the rule of thumb and the explanation to follow:

pixel dimensions ÷ 250 = largest size in inches at which you can print

This is regardless of the resolution of the image.

### Explanation

When searching the web for images for printing, there are a few extra things to keep in mind other than pixel dimensions (width by height). For printing, an image should ideally have a resolution of 250 pixels per inch. This means that for every inch of space you want your image to occupy on the printed page, there should be 250 pixels of information. For example, an image which is 1024 x 768 pixels would look best if printed no larger than 4.1 x 3.1 inches (roughly 4 x 3). How do we figure this out??

1024 pixels ÷ 250 ppi = 4.096 inches
768 pixels ÷ 250 ppi = 3.072 inches

### Photoshop and image size

A common mistake that many people make is misinterpreting the information they read about the size and resolution of an image once they've downloaded the image and open it in Photoshop. When in Photoshop, under the Image menu one can view Image size. This dialog box will tell you the pixel dimensions of an image, and below this, one can also see the document size in inches. Many people look at the document size and immediately read this as the size at which they can print the image and they assume it will turn out looking good. This is only the case if your resolution is 200-300 ppi.

For example, this image was downloaded from the web, has a resolution of 200 and the document size reads as 1.97 x 2.5 inches. Ideally, one wouldn't not print this image any larger than the document size.

This image was also downloaded from the web, has a resolution of 72 and the document size reads roughly 4.6 x 7 inches.

The difference in the document sizes of these two images is almost 3x. However, according to our rule above, we don't want to print this image at 4.5 x 6.9 inches because we have only 72 pixels of information per inch and our image won't look so great. Ideally, we wouldn't print this image any larger than 1.3 x 2 inches. This way we'll have 250 pixels of information per inch. An image of this size is okay for a small illustration within a text, but if you're seeking to print larger images to accompany your text, we suggest finding a larger image on the web or scanning an image from a book.