Dealing with grids in Photoshop is a pain
With GuideGuide, it doesn’t have to be. Pixel accurate columns, rows, midpoints, and baselines can be created based on your document or selection with the click of a button. Frequently used guide sets can be saved for repeat use. Grids can use multiple types of measurements. Honestly, if you haven’t started downloading it by now, you’re probably a masochist. Weirdo…
Download and unzip GuideGuide.
Launch the Adobe Extension Manager.
Windows Users: You may need to run the Adobe Extension Manager as Administrator (right-click the Adobe Extension Manager icon and click “Run as Administrator”).
Click Install and navigate to the GuideGuide extension file (.zxp).
You should now be able to find GuideGuide at Window > Extensions > GuideGuide