The basic question that many amateur photographers ask is, "How many megapixels do I need?" The answer to that question is that it depends what you want to do with the picture. The more megapixels you have, the crisper your image will be.
If you're planning to share the pictures on the Web, a lower resolution will be fine. However, if you're planning to enlarge a picture, then you will need a higher resolution [source: CNET]. Let us now understand the relation between resolution and print size.
- A megapixel is one million pixels. Megapixels are like the building blocks of a digital camera. The more megapixels you have, the better the quality the picture will be and the more you can enlarge your picture without compromising clarity.
- A camera with 4 or more megapixels will enable you to make poster-size pictures without compromising the picture's clarity. You will easily be able to make a 5-inch-by-7-inch (13-centimeter-by-18-centimeter) print or an 8-inch-by-10-inch (20-centmeter-by-25-centimeter) print with a 4-megapixel camera. However if you're taking pictures that you want to print as standard 4-inch-by-6-inch (10-centimeter-by-15-centimeter) prints, then using a 2-megapixel camera will suffice [source: Kodak].
There are tables online, which can help you figure out how large a print you can make with your camera, without sacrificing the clarity of the image. All you need to know is the number of megapixels your camera has.