When one questions how big is a photo 4x6, they usually think that it is just used in casual prints. According to Visuals Clipping, the photo 4x6 can be used not only in the cases of personal prints, but also in the case of professional proofs, contact prints, or small promotional materials. This size is not ideal with regards to detailed displays, but it is useful with regards to previews, handouts, and where small and clear images are required.