The Google Maps app will display a dynamic scale every time you zoom in or out of a map. The values present on the scale give important information about your current zoom level (such as the altitude and distance). This simple trick will teach you how to permanently display the scale bar in Google Maps for Android.
Always Show the Scale in Google Maps for Android
Open Google Maps, tap the Menu button, and select Settings.
Next, tap Show scale on map, and select Always:
The scale bar will now be shown on all of your maps: