Use your phone as a Ruler. This Ruler app supports three types of scales: metric ruler, inch ruler, fractional ruler in inches. You can use a coin or a credit card to calibrate the scale, even if you don't have a real ruler handy!
It's free of charge to download the installer of Ruler, also, you can have a look at users' reviews on Droid Informer. The app runs on Android 3.0 and above. This application is totally secure to download. Dim&Pav is the developer of Ruler that is included in the Tools category.
The most recent release was on Dec 22, 2016 and the app was downloaded and set up by over 100K users. The average user rating of this application is 4.4. Advertisements are a part of Ruler.