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On Display

Dpi stands for dots per inch, and it refers to the printing process. More specifically, it reveals the number of ink dots a printer will place on the page when it prints an image.

Ppi refers to the number of pixels per inch in a digital image file. An image’s ppi (also

Whether you're talking dpi or ppi, if you don't have enough, your image will be lousy. Just like all good things in life, there's no such thing as too much. You can always make an image smaller.

referred to as resolution or pixel density) affects how large the image will print out and how good its quality will be.

To determine the size an image will print to, simply divide its number of pixels by its ppi. For example, a 1000 x 1200 pixel image printed at 200 ppi would print out as 5 x 6 inches (or, 1000/200 x 1200/200).

Ppi and dpi numbers do not directly correspond to each other because a printer may use several dots of ink to reproduce one pixel. However, they do have one thing in common: “The higher the ppi or dpi number is, the more dots or pixels are compressed in an inch, and the better the image’s quality is,” says Dan Riley, president of Dysgraphic by Design in Louisville, Ky. “Higher numbers mean cleaner, crisper images.”

Although all printers are different and not all pixels are created equal, a good rule of thumb is to figure 3 dots per pixel. So a 1200 dpi print would be roughly equivalent to a 400 ppi image.
Formula One

Surprise! As it turns out, math is important in real life. When it comes to turning that cute logo on your Web site into a poster-sized display, you’ll need to know how to keep the dimensions in proportion. Otherwise, you can end up with some serious stretchage.

If you don’t want to flex your math muscles at this point in your life, try this proportion calculator. Simply plug in the original dimensions and the reproduction dimensions, and you’ll discover the percentage you’ll be increasing your starting image.

The calculator also works if you have the original dimensions and reproduction percentage and want to calculate what the image’s new size will be. Also be sure to check out the convenient DPI calculator on the bottom of the page.