How to create grid in GIMP (not sure if the filter is good)

I'm a beginner to GIMP, and I'd like to create a grid.

I searched Google and all it gave me was to use the Filter > Render > Grid plugin, but for my job all I want to do is something like this:

Let's say I have a square image that's 1530 x 1530, and I want the grid to be an 8 x 8 matrix with grid lines that are 1px wide. I don't want to calculate the right spacing on each grid cell as the grid filter gives me; I just want GIMP to calculate the right spacing and grid line width for this image.

Is there a way to do it right?