Just need some help

[drowofluna]

This may be common knowledge, but im new to it.  I need to create a grid for a template i need to print.  Im having issues putting the guidelines exactly where i need them.  Is there a way to specify in inches on where i need the lines? I have discord or whatever just to get help it would be greatly appriciated.

[rich2005]

Gimp works in pixels,  not inches / centimetres / points

The equivalence is determined by a pixels-per-xxx setting traditionally pixels-per-inch (PPI) although in Gimp you might get pixels-per-millimetre and have to select PPI.

With your template open, look in Image -> Print Size which gives the PPI value. 

What can you do for guides

Use a grid. Set one up on a per-image-basic Image -> Configure Grid  When you Save (as a .xcf) that setting remains for that image. As an example: This is 300 PPI I can set a grid for 1/8 (0.125) inches and you can see that the pixel spacing is 37.5 pixels, so a grid line might be half a pixel off. The same applies to values like 0.266 inches = 79.8 pix. that ends up as 80 pix. Use the grid to position the guide, Image -> Show Grid toggles on / off.

   

How can you place odd value guides, One way is the measure tool https://docs.gimp.org/2.10/en/gimp-tool-measure.html see the Key Modifier section. Truthfully this is not easy. A work-around is using a rectangular selection, enter values for the origin (0,0) and the dimension required, then use Image -> Guides -> New Guides from Selection You get some 'extras' on the edges but it works.

   

All that is a GUI way, you can use a calculator and determine pixels values PPI x dimension and place them using Image -> Guide -> New Guide

Just a note: I seem to recall some services such as Amazon Printing have ridiculous requirements, Margins with 4 decimal places. All set up for Adobe Illusrator, which is a vector program, the best you get with Gimp is the closest pixel. The difference is tiny.