Grid settings

Have a basic idea of the area/volume of the objects I want to sketch. I would like to set the scale so it is at a given increment…say 1ft. I zoomed out so the visible working area is about what I want (~100ft). How can I set the grid so it will be at 1 ft increments? I can’t see, to get anything but 4ft 8ft … as I zoom in and out. Most of the individual component sketches will only be around 4ft max so they’ll fit ok at 1ft grid. Can’t figure it out.

I don’t see the problem

Same thing on a mac. Just zoomed to 1ft and locked.