How many megapixels do I need?

As a photographer, I get asked about cameras from time to time. One question has to do with how many megapixels are needed to get a decent print. My answer is generally that megapixels do not matter as much as other features of a camera. It is only valid when you want to print extra large sizes where it starts to be a factor (or also for big crops but that will degrade resolution and print size).

Generally speaking any recent camera that has 5 megapixel or better resolution will do fine in the common sizes such as 4x6 and 5x7. Even when you get to 8x10 it is hard, or almost impossible to tell the difference between at 5mp and 10mp camera.

Thom Hogan wrote a very good article and chart on this subject, that might be helpful to help you understand the relation between megapixels, resolution (dpi) and print sizes.