Ruler, developed by keuwlsoft, is a simple yet useful app for anyone who needs to measure things on their Android device. This on-screen ruler is free, ad-free, and requires no special permissions. The app automatically sizes to most screens, but users should check the scaling with a normal ruler on the first use to ensure accuracy.

The app offers both centimeters and inches as measurement units. Users can measure the length between two markers and copy the measurement to the clipboard. Ruler is a straightforward and convenient tool for anyone in need of quick and accurate measurements on their Android device.