Ratio Calculator
Solve proportions, find missing values, simplify ratios, and compute scale factors.
Proportion: A : B = C : D (leave one field blank to solve)
Result
Missing Value
Simplified Ratio
Scale Factor
What is a Ratio Calculator?
A ratio calculator solves proportion problems of the form A : B = C : D. It can find a missing value when three are known, simplify ratios to their lowest terms, and determine the scale factor between two ratios.
How to Use
- Enter three known values into fields A, B, C, and D.
- Leave exactly one field blank—the calculator will solve for it.
- Click Calculate to see the missing value, simplified ratio, and scale factor.
Frequently Asked Questions
How is the missing value calculated?
The calculator uses cross-multiplication. For A : B = C : D, the equation is A × D = B × C, and the missing value is isolated algebraically.
What is a scale factor?
The scale factor is the constant ratio between corresponding terms, calculated as C ÷ A or D ÷ B.
Can ratios include decimals?
Yes, this calculator supports decimal and fractional values in ratios.
Is this calculator free?
Yes, BestCalc calculators are completely free and run entirely in your browser.