Popular Sizes:Letter size: 8.5 x 11 inches (2550 x 3300 px at 300 DPI)Art prints: Sizes can vary, but 11 x 14 inches (3300 x 4200 px at 300 DPI) is popular.Postcard size: 5 x 7 inches (1500 x 2100 px at 300 DPI)Poster size: 18 x 24 inches (5400 x 7200 px at 300 DPI)