I've briefly talked about the size of wall art in the past, but today we will dig a little deeper into the subject.
You want the overall look of your room to be balanced. If your artwork is too large for the available space it will take over the room. Going in the opposite direction imagine hanging a 5 x 7 photo over the couch. It would get lost and not seen.
When you set off to buy your artwork decide where it will be hanging in your home. Measure the width of the available space. To determine how large your artwork should be you will want to use the three-eights rule. What this means is that generally you want your artwork to leave an empty space equal to three-eights of the width of the photo on each side. Ok, I can see your eyes glassing over with that last sentence.
What this all means is that you can figure out the perfect size photo to hang on your wall by multiplying the width of the wall by 0.57. The result will be the size of the photograph you should hang in that space.
Recap: Available space width x 0.57 = art size.
Don't forget to include the size of the frame. Although it doesn't sound like much, a simple two inch frame will add 4 inches of width to your photograph or artwork. Don't worry if you go a little over or under on the size. I don't think anyone is going to come in and measure it. Just stay as close as you can to keep the look of your room in balance.
One last thing to remember when hanging your artwork. Hang the artwork so the center of it is about 65 inches from the floor if it is an open space. If you are hanging the piece above a table or sofa keep the bottom edge at least 9-12 inches above the piece of furniture.