Proportion Calculatorv1.0.0

Find missing values and verify ratios quickly with this online proportion calculator. Enter three known values in the equation A : B = C : D to solve the fourth value, or enter all four values to check whether the relationship is proportional. View instant results that include simplified ratios, percentage differences between the two ratios, and a clear step-by-step explanation. Use this tool to support math practice, budget comparisons, recipe scaling, model design, and other tasks that require reliable proportional reasoning.

A proportion states that two ratios are equal. The relationship A : B = C : D is equivalent to A/B = C/D and to the cross-multiplication identity A × D = B × C. The calculator uses these identities to solve for a missing term or to confirm that four values form a valid proportion. Reduced ratios express the same relationship using the greatest common divisor to provide the simplest integer pair.

Proportions: A : B = C : D Equivalent to A / B = C / D Or A * D = B * C Ratio Reduction: For ratio a : b, divide both a and b by their greatest common divisor (GCD). Percentage Difference: | (a/b) - (c/d) | / ( (a/b + c/d) / 2 ) * 100 

Solve a missing value or verify a proportion with clear, step-by-step outputs.

• Enter any three values in A, B, C, and D. Leave exactly one field blank to solve it, or fill all four fields to check if they are proportional.
• Use integers, common fractions (for example, 3/4), or decimals with up to two places (for example, 2.5). Include a leading minus sign to enter negative values where appropriate.
• Click Calculate to compute the missing value using cross-multiplication or to test whether A : B equals C : D.
• Review the Solved value, the Check result, reduced ratios for A : B and C : D, the Percentage Difference between ratios, and a Steps breakdown.
• Use Reset to clear inputs and results. Rely on automatic formatting for readability, and return later to your last session through saved values.
• Share or reproduce a calculation by adding URL parameters ?a=, b=, c=, and d= as needed.

Apply proportional reasoning to compare quantities, scale values, and validate relationships across everyday and professional tasks.

• Education: Practice solving A : B = C : D problems, check homework, and confirm reduced ratios and equivalence.
• Finance: Compare price-to-value ratios, normalize benchmarks across portfolios, and analyze cost comparisons.
• Cooking: Scale recipes up or down while preserving ingredient ratios and tasting consistency.
• Engineering: Verify scale models, confirm gear or pulley ratios, and validate tolerance relationships.
• Data Analysis: Normalize metrics across categories, compare conversion rates, and assess relative performance.
• Mapping and Design: Convert map scales and maintain layout proportions when resizing assets.

Work through common scenarios to see how the calculator helps.

• Price comparison: If 3 items cost 18, find the cost of 7 items. Enter A=3, B=18, C=7, leave D blank. Calculate to solve D.
• Recipe scaling: If 2 cups of flour match 1 cup of milk, find milk for 3 cups of flour. Enter A=2, B=1, C=3, leave D blank to solve D=1.5.
• Model scale: If 1 cm on a map equals 4 km, check whether 3 cm equals 12 km. Enter all four values and use Check to verify.

What formats can I enter? Enter integers, fractions like 5/8, or decimals with up to two places. Use a leading minus sign for negative values when the context allows.

What happens with zeros? The calculator prevents division by zero. If B or D is zero when forming a ratio, the tool flags the issue and does not compute the result.

How are results rounded? The input field for a solved value displays a rounded figure for readability, while internal steps keep precise fractional values to maintain accuracy.

Can I only check proportions? Yes. Fill all four fields and click Calculate to confirm whether the values satisfy A × D = B × C and to view percentage difference when they do not.