Ruler is a free Android app developed by DimPav that allows you to use your phone as a ruler. It supports three types of scales - metric ruler, inch ruler, and fractional ruler in inches - making it a versatile tool for measuring objects.

One of the app's standout features is its ability to calibrate the scale using a coin or credit card, which comes in handy if you don't have a physical ruler available. The app is easy to use and provides accurate measurements, making it a convenient tool for anyone who needs to measure objects on-the-go.

Overall, Ruler is a useful app that provides a simple solution for measuring objects using your phone. Whether you're a student, DIY enthusiast, or just need a quick way to measure something, Ruler is definitely worth checking out.