Scale measure

[Krikor]

I found these two sites very useful:

Virtual scale ruler -
https://www.ginifab.com/feeds/cm_to_inch...ruler.html?

Pixels Per Inch PPI Calculator -
https://www.calculatorsoup.com/calculato...ulator.php

As a result of reading these sites I was able to create a virtual rule that visually converts pixels to the metric scale.

The ruler created on the website is available for download and can be used, for example, as a brush or pattern in GIMP to be used as a metric reference.
   
I found the result quite satisfactory.