What's the resolution?

A picture is 800 pixels wide and 574 pixels high.

It prints very small at 2.67 inches wide x 1.91 inches high.

Photo of lutenist Ronn McFarlane, © 2004 William R Schneider - All Rights Reserved

What is the resolution of this picture, and why does it prints so small?

Solution

We know the number of pixels in the picture (both width and height), and we know the print dimensions of the picture. We can calculate the resolution by dividing the pixels by the print size on one edge of the picture.

Width = 800 pixels / 2.67 inches =  ~300 pixels per inch (ignoring a little rounding error)

Because resolution is the same in both width and height, calculating it on one edge is sufficient. However, it sometimes serves to double-check your math to do the other dimension.

Height = 574 pixels / 1.91 inches = ~300 pixels per inch (ignoring a little rounding error)

This check out along both edges, so we're fairly confident in our answer.

And, yes, this picture will print small because the resolution is high. With any fixed number of pixels in a picture, higher resolution results in a smaller print. When resolution is increased, the pixels become small (more of them fit in an inch), therefore the picture must shrink in size too.