DPI. A common question among many small business owners is how to tell if their picture is the right size for reproducing on a flyer, business card or brochure. The term "dpi" stands for "dots per inch", and is a term that has been around for a long time for printers. It refers to the number of ink dots a printer puts on a piece of paper. Unfortunately due to its legacy, it's often mis-used in communications, for instance when your printer or designer asks for an image that will print at 200 dpi. Your image is a digital image, so you don't have a printer's "dpi" to measure.

PPI. The term you're really looking for is "ppi," which stands for "pixels per inch." If you look at an image on a website, you can typically right-click on the image and it will tell you the dimensions in pixels. For instance, the image to the right is 200 pixels wide by 240 pixels tall. So what's the ppi? Well, that depends on where you'll be using it. A typical monitor displays 72 ppi, so this image has been re-sampled down from a big image to the size (200x240) and a ppi of 72 pixels per inch. This gives you the best quality at the lowest file size, making it load quickly on the page. But let's say you copy that image and try to print it on your local color printer. What appears to be about 2 x 2.5 inches and sharp detail on the screen will print differently on your printer.

If you print the image at 72 pixels per inch on your printer, it will be about the same size. However, it will have a pretty poor quality, very pixelated (jagged edges). If you print it at the recommended resolution for your printer, let's say 200ppi, it will have a better quality producing a sharper image, but it's going to drop down to less than half the size you see it on the screen. That's because you still have the same total number of pixels in your image (200x240), but you're cramming them into a smaller space to produce a sharper image.

How to tell if your image is big enough to produce a sharp image with the quality you want: First check with your printer or designer, find out what size it's going to be on the printed document, and at what resolution they want it. Most printers will want a minimum of 200 ppi, but 300 ppi will produce a sharper image. So let's say your image will be 3x4 inches on the brochure, printed at a sharp 300 ppi. That means you need 300 pixels per each inch: 3 inches times 300 pixels per inch means your image needs to be at least 900 pixels wide; 4 inches in height times 300 pixels per inch equals 1200 pixels tall. Next, verify the size of your image (right click on it to see the properties). Is your image at least 900x1200 pixels? If yes, it's large enough. If it's less in either dimension, it will either be printed with poor quality, smaller size, or both.