Rule of 3 Calculator is described as 'Portable tool that allows you to apply the mathematical Rule of Three in an easier, faster and more practical way!' and is a Calculator in the education & reference category. There are more than 100 alternatives to Rule of 3 Calculator for a variety of platforms, including Android, Windows, Mac, iPhone and Web-based apps. The best Rule of 3 Calculator alternative is Wolfram Alpha, which is free. Other great apps like Rule of 3 Calculator are SpeedCrunch, Fossify Calculator, Qalculate! and OpenCalc.