# Proportion Calculator

> Solve a proportion A : B = C : D for one missing value using cross multiplication. Returns the missing value and the worked step.

**URL:** https://www.calculatoranswers.com/proportion-calculator
**Category:** Education

## Quick Answer

Solve for unknown values in proportion equations. Enter three known values in the ratio fields to calculate the missing term using cross-multiplication.

## Definition

A proportion calculator is an algebraic tool that solves for an unknown value in a proportion equation of the form a/b equals c/d. When any three of the four variables are provided, the calculator uses cross-multiplication to solve for the missing variable. It can also verify whether a given pair of ratios form a true proportion by cross-multiplying and comparing the products. Students, chefs, and designers use this tool to scale recipes, adjust design dimensions, and solve ratio-based word problems.

## How to Use

1. **Set up the proportion** — Identify the four fields representing the numerator and denominator of the two ratios.
2. **Enter known values** — Type three known numbers into the appropriate fields, leaving the unknown variable blank.
3. **View the solution** — Read the calculated value of the missing variable along with the cross-multiplication steps.

## Disclaimer

This calculator provides estimates for educational and planning purposes. Always consult a qualified professional for specific advice on financial, medical, legal, or other regulated decisions.

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