Let’s start with a simple problem. Let’s say we have three paintings that have to fit, evenly spaced, on a wall that is 100″ wide, which has no additional features or obstructions. We’ll also assume the height of the wall is of an average height (10′), and is thereby sufficient for a standard method of hanging. For the sake of this discussion, we’ll say these three paintings are 16″ high x 20″ wide.
Horizontal Placement
First, we’ll find the horizontal placement for these pieces, by subtracting the total width of all three paintings (20″ + 20″ + 20″ = 60″) from the total width of the wall (100″ – 60″ = 40″). Now we divide that 40″ by 4, to give us an interval between the paintings of 10″. This means that from the edge of the wall to the paintings is a space of 10″ and between each painting is also a space of 10″. to simplify this as a formula, we might write it as such:
(Width of wall – Combined Width of all paintings) / (No. of total paintings + 1) = Interval Distance
Using the dimensions above, the formula would look like this:
(100″ – [20″+20″+20″] ) / (3 + 1) = 10″
Vertical Placement
To calculate where to place your nail or screw (or the bottom of the hook when using hooks and nails), we use the following formula:
Total Height of Work / 2 + 60″ – Offset
Using our figures, this gives us the following:
16″ / 2 + 60″ – 2″ = 66″
This means we have to put the anchor at 66″ from the floor in order for the center to be at 60″ or eye level.
Calculate Spacing Between Frames
For best results center the frames 60 inches (152 cm) from the ground.
Source and more visualizations here:
http://sageartsstudio.com/wp/blog/2012/10/20/how-to-hang-a-show/