The question of how many magapixels one needs in printing comes up all the time, and there’s a real range of opinion about it. Let’s keep things simple. Shoot for 300 pixels/dots per inch for the best print quality. Go down to 224 or even 200 pixels per inch if you have to, and you’ll still probably be okay. Sometimes you can go even lower, depending on the print medium and the nature of the image.

The chart linked below and at right does only one thing: it tells you how many pixels fit in images up to 20 x 20 inches at 300 pixels/inch. The outer level is inches. The next level is inches times 300. Those products are multiplied for the various vertical and horizontal lengths to show how many pixels the area represents. For example:

Now, I’m not going to tell you how to use the chart, so don’t send angry e-mails telling me your camera does much better than this and I've fallen for "the megapixel myth," which is a capitalist scheme to get everyone to buy more camera than they need. What I'm giving you is just plain raw numbers: simple arithmetic determining how many dots fit in a given area at a given density. Obviously at 200 dpi your megapixels are only 44% what they are at 300 dpi (an image 1 x 1 at 300 dpi is 900 pixels; at 200 dpi it is 400 pixels; two thirds times two thirds is four ninths). So you can probably safely cut your megapixels at least in half from what is shown on the chart.

Some people are always going to insist that they get excellent 8 x 10s from one-megapixel images. To do that they would need to print at about 112 dpi (112*8=896; 112*10=1120; 896*1120=1,003,520). If you’re good with that, fine, feel free. (Me, I'd rather be at 300, and at least not below 200.)

Click here for the chart (pdf format).