Rule of Three Calculator
Solve proportional problems
How to Use
Enter three values (A, B, C) to find the fourth using the rule of three: if A gives B, then C gives D.
Frequently Asked Questions
What is the rule of three?
The rule of three is a mathematical method to find an unknown value in a proportion: D = (B × C) / A.
When is it used?
It's used when you know three values in a proportion and need to find the fourth.