If you are interested in knowing how big is a 4x6 photo, it is 4 inches by 6 inches, which is smaller than a 5×7 photo. The advantage of the difference is, as Visuals Clipping states, that it provides the 5x7 format with a larger viewing area, which is not the case with 4x6 that provides a smaller, more convenient viewing area for albums and smaller frames. Both sizes are used for personal pictures, but they are used for slightly different purposes. Deciding between these can relate to space, framing preferences and the prominence of the image.