Do I Make Graphic Design for Print Size Correctly?

[Blighty]

(12-10-2017, 09:35 AM)TechnicGeek Wrote: Does it matter whether I set new image as 15" or 15cm when it comes to calculating resolution? Will 10x10 x 300 DPI be same with " and cm?

You mean even scaling down from high DPI causes degradation?

You need to remember: Gimp works in pixels, not dpi.

A 15"x15" image @ 300 dpi will give a size of 4500x4500 pixels
A 15cm x 15cm image @ 300 dpi will a size of 1772x1772 pixels.
You need to get the size in pixels correct right at the start.

Scaling does not change the dpi. It changes the size in pixels. Scaling will throw away (or create) pixels as required. This causes degradation.