Proportion Calculator

Solve proportions in the form x / y = a / b. Leave exactly one field empty and the calculator will find the missing value, show the exact fraction, decimal form, reduced ratios, and the cross-multiplication steps.

Equation Input

Supported formats: decimals, negative numbers, comma decimals, and simple fractions like 3/4. Denominators y and b cannot be zero.

Rule: fill any three fields, leave one empty, then solve. The result updates automatically in live mode.

Decimal precision

Missing field

Result

The calculator uses exact rational arithmetic whenever possible, so fractions stay precise instead of turning into unstable floating-point values too early.

Waiting for input.

Solved value

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Exact fraction

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Reduced ratios

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Cross products

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Left side

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Right side

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Cross-Multiplication Steps

The calculator shows which variable was solved and the exact algebraic substitution that was used.

No calculation yet.