I used the 3x5 but then I also did some manual cropping. I picked my size then I took the corners of the picture and made the picture smaller again by moving them in. For me it was trial and error whether it would fit, but this was my first time posting a picture. As you can see by my picture it is still overly large but it was less than maximum download size so it worked. I am going to see if there is an app like photoshop to do it better and let you know.