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Math Calculator Hub

Accurate mathematical tools for proportions, ratios, statistics, and more. Reverse-solve any formula — enter the values you know, get the value you need.

Full Double-Precision Client Computations

Available Math Calculators

Math

Proportion Calculator

Solve any proportion (A/B = C/D) for a missing value, calculate sample proportions in statistics, and apply proportions to a population. Free, instant, and accurate.

Formula:A/B = C/D → D = (B × C) ÷ A

4 Mode Dynamic SolverLaunch Tool

Peer-Reviewed Mathematical Standards

Every formula in our math calculators is sourced from established mathematical standards and peer-reviewed references. Proportion calculations use the cross-multiplication rule (A × D = B × C); sample proportion follows the statistical definition p̂ = x/n used in inferential statistics.

Read full methodology specifications

Proportion ruleA/B = C/D → A×D = B×C

Sample proportionp̂ = x ÷ n

Solving modes4 (A, B, C, or D)

Precision: All calculations run in double-precision floating-point arithmetic directly in your browser. No data is transmitted to any server.