Scale Calc ulator makes it clear how to convert the size of the area on a map or drawing to the model and back on the scale. Without advertising. The Internet is not required! Examples of scale: The scale of the decrease. 1: 2. 1: 2. 5. 1: 4. 1: 5. 1: 10. 1: 15. 1: 20. 1: 25. 1: 40. 1: 50. 1: 75. 1: 100. 1: 200. 1: 400. 1: 500. 1: 800. 1.