I sell fine art images online, as well as prints from portrait sessions, and many times people order an image in a size that doesn't suit that particular image.
Aspect ratio is the relationship of an image's width to height, or its proportions. Digital cameras produce files with an aspect ratio of 4:3. But many common photo print sizes have a different aspect ratio. For example, a 4 by 6 print has an aspect ratio of 3:2; an 8 by 10 has an aspect ratio of 5:4.
I've put together a little visual comparing the differences, hoping to take some of the confusion out of why the image you see in an online gallery will look different when it's printed.
When I have someone order something in a size I don't feel will work for an image, I always do a little crop screenshot in photoshop and send it in an email to my client.
Thanks to my friend and fellow photographer Sacha Blue for sharing this template below.
I hope you find this info helpful....and please share to your facebook page if you do. There's a handy dandy little share button down on the bar at the bottom!