I am not a big fan of grid for sketching in FreeCAD I use it when I have to sketch a part profile whose enough detail dimension is not available previous sketch grid in FreeCAD has resizing issue and it was only available in Draft Workbench. At the time of writing this post I am using FreeCAD 0.20.2 and I do not see sketcher grid As you can see in image it is a upcoming feature in FreeCAD 0.21.0. It is good to see that FreeCAD development team adding new feature to FreeCAD With a redesigned user interface for turning it on and off and adjusting the scaling parameters, the grid view in the Sketcher Workbench has undergone a significant refactoring.
It now incorporates automatic resizing as you zoom in and out. As shown in Image you can set custom spacing for Grid under sketcher workbench.
The final result is a modification that affects more than 10,000 lines of code distributed over 36 files. The underlying modifications should make the Sketcher code base more flexible and manageable, while the grid’s automated rescaling improves the user experience significantly.
I would like to thanks developers @PaddleStroke, 
Posted from my Blog Mechnexus.com with Exxp : https://mechnexus.com/setup-auto-spacing-in-freecad-sketcher/