Hang your paintings like they do in art galleries and museums.
You've acquired a wonderful piece of fine art that needs hanging on a wall. Here's what you do.
Always hang the art at 57" on centre. This means that the middle of the painting will be at 57". Why 57"? Art galleries and museums regularly use this as a standard because it is the average height of the human eye. By using this standard all pictures hung on your walls will have the perfect view in relationship to each other based on their centres, alleviating the problem that some people have of hanging too high.
How to go about it?
1. Measure up from the floor to 57" and put a light mark with a pencil.
2. Measure top of the picture to the middle (or take height and divide by 2)
3. Measure top of the picture to the tightened wire
4. Subtract this last amount to tell you how far above 57" your hook should go
5. Measure up from 57" with this last amount and lightly mark on the wall
So, if the painting is 20" tall, the middle would be 10" (which is where 57" from the floor will be). If the wire comes below the top of the painting at 2", then 10" minus 2" equals 8". So lightly mark 8" above your initial mark. This would be 65" from the floor.
Sounds complicated but it isn't. The key is to remember that the centre of all your paintings is set at 57" and all you're figuring out is where to put the hook.
[taken from Apartment Therapy]