Using GIMP: Correcting and Touching Up Your Images - GIMP 2.6 for Photographers: Image Editing with Open Source Software - page 86

Figure 2.23
The navigation window

2.3.6 Setting the Image Size and Resolution

• NOTE
As mentioned earlier, you can find
all necessary commands in the
working menu located on the menu
bar above the image as well as in the
context menu, which opens when
you right-click on the image. If you
prefer working with your mouse,
the context menu should be easier
and faster to use. However, if you
prefer to work with the keyboard,
you'll probably want to use the
keyboard shortcuts. Keyboard
shortcuts are displayed next to
the corresponding menu items.

Before we talked about changing the view size of the image, it had already
been rotated. So the image should be upright now. Next, you'll want to set
the size and resolution.
Let's say you want your image to be the size of a photo print, 13.5 cm x 18 cm,
about 5 in x 7 in, so it can easily it on one print page. The target resolution of
the image is 300 dpi.
Options for setting the size and resolution are located in the image
window; just choose Image > Scale Image .
When the Scale Image window pops up, you can set the measurement for
X resolution to 300 pixels/in (= dpi). In the text field, just overwrite the default
value and press Enter to accept your changes. Both resolution values should
now be 300 pixels/in.