What is the difference between direct and inverse proportion?

In direct proportion, increasing one value increases the other proportionally (e.g. recipe ingredients); in inverse proportion, increasing one decreases the other (e.g. speed vs travel time).

Can I enter decimal numbers?

Yes, the calculator accepts decimals and provides both exact fractional and decimal results.

How do I scale a cooking recipe using proportions?

Set A as original ingredient amount, B as original servings, C as unknown new amount, and D as target servings.

Mathematics Tools• Cross Multiply

Proportion Calculator & Cross-Multiplication Solver

Solve for any unknown variable X in equal ratios (A/B = C/D). Perfect for recipe scaling, map scale conversions, model building, and algebraic fractions.

Calculations run client-side. Zero data sent to servers.

Term A

Term B

Term C

Term D (Unknown)

Solved Value for D

D = 50

Cross-multiplication solution verified

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How to Use Proportion Calculator (A/B = C/D)

Enter Known Values

Fill in three known values for A, B, C, or leave one empty as X.

Select Relationship Type

Choose Direct Proportion (as A increases, B increases) or Inverse Proportion.

View Solution

Inspect the calculated missing variable with step-by-step cross-multiplication algebra.

About Proportion Calculator (A/B = C/D)

Applies the fundamental property of proportions: cross products are equal (A * D = B * C). Solving for unknown X isolates the variable via basic algebraic division.

Supported Formats

IntegersFractionsDecimals

Operational Limits

•Denominator values (B and D in direct proportions) cannot equal zero.

Key Features

Solves for any missing term (A, B, C, or D)
Supports both Direct (A/B = C/D) and Inverse (A * B = C * D) proportions
Full step-by-step algebraic solution display
Fraction simplification and decimal equivalent outputs
One-click copy of results

Frequently Asked Questions

Cross multiplication multiplies the numerator of each side by the denominator of the opposite side (A*D = B*C) to solve for an unknown value.

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