Ratio Calculator
Solve proportions by entering three known values to find the fourth. If A:B = C:D, enter A, B, and C to calculate D automatically.
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Missing Value (D)
Enter values to calculate
How to Use the Ratio Calculator
1
Enter value A and value B (the known ratio).
2
Enter value C.
3
View the missing value D.
Frequently Asked Questions
How does the ratio calculator work?
It uses cross-multiplication: if A/B = C/D, then D = (B × C) / A.
Can I use decimals?
Yes — the calculator supports integers and decimals for all values.
What are common uses for ratios?
Ratios are used in recipes, map scales, mixing solutions, currency conversion, and resizing images.