D.P.I. or “Dots per Inch” is the measurement used within the printing and graphics design industry to determine how sharp an image is. Web graphics and online photos are normally created at 72dpi (dots per inch). This low resolution is great for the web because the images look excellent on a computer monitor and the file sizes are very small which helps web pages load faster. However, when designing graphics for commercial printing purposes, your images should be 300dpi or better, here’s why.
Essentially, the difference between 300dpi and 72dpi is found in the amount of pixel information (or dots) for every square inch of the image you are viewing. The more dots/pixels the image contains, the sharper the image will print. As a result, printing will look blurry if a 72dpi image is used as compared to using a 300dpi high resolution image.