How can I make a file 300 dpi?

You can change an image’s DPI in most graphics packages. You can even do it in Preview on a Mac, but we’ll mention basic three solutions that will have you covered on any platform. Remember that DPI is only a measurement of print resolution. Changing the DPI does not change the size of your digital image or the size of the file. If working with an image you think you’ll need to print, it’s a good idea to set your target print resolution before you resize it. That will help to ensure you don’t make it too small to print safely at your preferred size. How to Change the DPI in Photoshop. To change an image’s DPI in Photoshop, go to Image Image Size. Uncheck Resample Image, because this setting will upscale your image, which will make it lower quality. Now, next to Resolution, type in your preferred resolution, and set it as Pixels/Inch. Notice how the Width and Height figures change, too. This shows you the size your image will print.