Checking an Image’s DPI
To find out an image’s DPI, right-click on the file name > Properties > Details. You’ll see the DPI in the Image section, labeled Horizontal Resolution and Vertical Resolution.
Change DPI Free Online
If you’re in a pinch and you don’t have your graphics program of choice on hand, you can always change the DPI of an image with Convert Town’s DPI-changing web-app, for free online.
All you have to do is input the DPI you need the image changed to, drag-and-drop the file to upload it, and wait. When it’s done converting, it should automatically download it to your default download folder.