DPI Calculator, developed by Duncan Leo, is a free Android app in the Utilities & Tools category that helps users calculate the DPI of their device based on its resolution and screen size. The app has a built-in list of common devices, which makes it easier for users to find their device and calculate the DPI accurately.

The app is straightforward and easy to use. Users simply need to select their device from the list, enter the resolution and screen size, and the app will calculate the DPI for them. The app also allows users to add custom devices to the list, which is a useful feature for those with less common devices.

Overall, DPI Calculator is a useful tool for anyone who needs to know the DPI of their device. The app is free, and the source code is available on GitHub for those who want to check it out.