About This Calculator
This calculator helps you solve proportions of the form A:B = C:D. By entering any three known values, it calculates the fourth unknown.
If you need to simplify a ratio, use the Ratio Simplifier Calculator.
How It Works
The calculator applies the proportion formula A/B = C/D. Depending on which value is missing, it rearranges the formula to solve for that unknown:
If A, B, and C are known: D = (B × C) ÷ A
If A, B, and D are known: C = (A × D) ÷ B
If A, B, and D are known: C = (A × D) ÷ B
Frequently Asked Questions
What is a ratio?
A ratio expresses the relationship between two quantities, indicating how many times one value contains another.
Can I input decimal numbers?
Yes, decimals are supported for precise proportional calculations.
What if I leave one of the fields empty?
You must provide exactly three values. The calculator will use them to compute the missing fourth value. Leaving more than one field empty will result in no calculation.