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CalculatorBuddy

Ratio Calculator

Solve an equivalent ratio from any three values or enlarge and shrink a ratio by a scale factor.

Enter any three values in A:B = C:D.

ExampleSample values — edit any field to see your result.

Results update as you type.

Equivalent Ratio

3 : 4 = 600 : 800

Estimated result

Missing Value
D = 800
Calculation
A × D = B × C
Equivalent Ratio3 : 4 = 600 : 800

Solve the missing value in A:B = C:D, or enlarge and shrink both parts of a ratio by the same factor. These two modes reproduce both forms on calculator.net.

Formula

Equivalent ratios satisfy A / B = C / D, so cross multiplication gives A × D = B × C. Scaling uses (A × k):(B × k) when enlarging and (A / k):(B / k) when shrinking.

Examples

Solve 3:4 = 600:D

D = 4 × 600 / 3 = 800, so the completed ratio is 3:4 = 600:800.

Shrink 250:280 by 2.5

Dividing both terms by 2.5 produces 100:112.

Frequently asked questions

How do I solve an equivalent ratio?
Enter any three values in A:B = C:D and leave the unknown value blank. The calculator uses cross multiplication to solve it.
What does scaling a ratio mean?
Scaling multiplies or divides both terms by the same positive factor, preserving the relationship between them.
Can ratios contain decimals?
Yes. The solver and scaling calculator accept finite decimal values as well as whole numbers.
Why must both sides use the same scale factor?
Applying the same nonzero multiplier to both terms keeps their quotient unchanged, so the ratios remain equivalent.

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