You don't. FW is a screen graphics app, not a print app. The only
useful measurement is pixels.
Thanks for that.
Just goes to show my Graphic's experience!
Is there a Adobe basic image editor that will do the job. Photoshop looks too intensive and expensive for my use.
Chances are that Adobe Photoshop Elements might be what you need, but
I've never used it myself. I'd recommend reading up on it or
downloading the free trial.
Images are rectangular blocks of data...how wide by how tall, and what color in each. Kind of like a spreadsheet, only...all you see is the color data.
The dpi or ppi (dots per inch or pixels per inch) is only important when you go to print an image, and even then, it depends on the output device and the use. When you print, you can stretch or shrink any image into any physical dimension. What you want to do is create an image that prints acceptably well at the size you want on the output device in question.
The basic formula is size (in inches) * dpi = pixels.
There are other factors to consider, however. For a high-resolution printer, you generally don't need to use the printer's dpi to produce an acceptable image. For instance, if you have a 2400 dpi printer, you could probably create an image using 600 dpi in your calculation and be happy. If the print is meant to be viewed at a distance, then you can use a lower dpi in your calculation than you might if you are producing something to be held in the hand and read. For example, a banner to be hung high in a large room, could probably be produced at 200 or even 100 dpi.
Summary. Image data is based on pixels and color information. It only touches physical dimensions when you output; you must incorporate the specifications of the intended output device and you should also consider how the piece will be viewed. Let go of the concept of a graphic file being a certain physical size. It isn't.