Rule of Three
Calculate simple rule of three proportions online with our free calculator. Find unknown values in direct proportions quickly and easily.
About this tool
The simple rule of three, also known as cross-multiplication, is a practical mathematical method used to find an unknown fourth value when you already know three values with a direct proportional relationship. Our calculator makes the process easy: whether you're scaling a recipe, calculating percentages, adjusting measurements, or doing homework, just fill in the fields with the known values and the calculator will automatically perform the calculation and show the result.
Features
Use Cases
- Scaling cooking recipes based on available ingredients
- Calculating fuel consumption for different distances
- Adjusting technical measurements and scale models
- Solving math problems and business proportion tasks
How to use
Enter Base Values
Input Value A and Value B to define your initial known proportion.
Enter Target
Input Value C to find its proportional equivalent (X).
Get Result
The result is calculated instantly. Use the copy button to send it to your clipboard.
The formula used is: X = (V3 * V2) / V1