How much bigger can I print a 10-megapixel photo than a 5-megapixel photo?
But they’re wrong. In fact, doubling the megapixels of a photo actually lets you add only 20 percent more area to each edge.
Here’s the math. A 5-megapixel photo might measure 1944 x 2592 pixels. When printed at, say, 180 dots per inch, that’s about 11 by 14 inches.
A 10-megapixel photo (2736 x 3648 pixels), meanwhile, yields a 180-dpi print that’s about 15 by 20 inches–under three inches more on each margin!