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Ratio Calculator

Calculate ratios and proportions.

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=
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How to Calculate

The ratio calculator solves for the unknown (?) in the form A:B = C:?. Formula: ? = (B × C) / A Enter three values A, B, and C to automatically calculate the fourth value in the proportion. The A:B ratio is also simplified to the smallest integer ratio.

Example

A:B = C:? 2:3 = 10:? Calculation: ? = (3 × 10) / 2 = 15 Result: 2:3 = 10:15

FAQ

Can I use decimal values?
Yes, decimal values are supported. Results are displayed to two decimal places.
What happens if A is 0?
Division by zero is not possible, so A must not be 0. Please enter a non-zero value.
How is ratio simplification done?
The greatest common divisor (GCD) of A and B is calculated, then each is divided by the GCD to produce the simplest integer ratio.