It drives me nutty when I see beautiful artwork hung so high you can hardly see it without throwing your neck out. The imbalance of proportion it causes when pictures are hung too high on the wall can be easily fixed. Once you see it at the right height, there's no going back. Hanging your artwork too high on a wall, which is fairly common, can also cause other issues such as increased glare from overhead lights.
So then, what is the "right" height? There's an easy rule of thumb for this that galleries, museums, and interior designers use to best highlight artwork. It's the rule of 57, although they say anything between 57 and 60" works. I prefer 60" as it leaves a bit more clearance for things in the home.
The mid-point in height of the artwork should be 57-60" off of the floor.
Ok great, so the hanging hardware is never at the half way point, so where do I put the nail on the wall? Let's use 60" for the eye level.
Measure the height of the artwork, and divide it by 2 for the midpoint of the artwork.
Add this number to 60"
Then pull the wire tight to the top of the frame, and subtract that from the total. That is where you put the nail.
Let's do this once more using actual measurements.
The artwork is a total of 30" in height.
30 divide by 2 is 15" This is where eye level will be
Add this number to 60 = 75"
Now, subtract the distance from the hanging hardware or wire pulled tight, to the top of the frame. Let's say the wire is 2" from the top of the frame when pulled tight.
75 - 2" is 73". So now, to get the picture to hang at eye level, you would put the nail 73" from the floor.
Knowing how to do this also helps get several same size pieces to hang at the exact height, as rarely is the wire exactly the same on each piece. Do this measurement for each piece, and voila, no more messing around moving the nail around.
This also works for gallery walls and groupings of photos to get the height. Simply treat the entire grouping as 1 measurement including the gaps. Of course, there is much more math involved. Will cover that at a later time.
For large pieces above a couch, or above waiting room chairs, you may need to increase the height just a touch. For above a couch, the bottom of the piece is fine anywhere from 6-8" above the couch, but don't go too far as it will look like it's floating, lost in space, above the couch and then you're back to being too high again. Keep it lower rather than higher. For the dental office above, I didn't want people banging their head on the bottom of the frame with so many people constantly sitting and standing, so I increased it just a touch. Very little. I had my tall helper sit and stand several times to see how low I could keep it.