# Proportion Calculator

Solve proportion equations of the form a/b = c/d and calculate the missing term

> Canonical page: https://elysiatools.com/en/tools/proportion-calculator

- **Category:** Math & Numbers

- **Keywords:** proportion, calculator, cross multiplication, ratio equation

## Overview

The Proportion Calculator is a straightforward utility designed to solve ratio equations of the form a/b = c/d. By entering three known values and selecting which term is missing, you can instantly calculate the unknown variable using cross multiplication. It is an essential tool for scaling recipes, resizing images, calculating map distances, and solving everyday math problems with precision.

## Inputs

- **First Numerator** (text): e.g. 3
- **First Denominator** (text): e.g. 4
- **Second Numerator** (text): e.g. 6
- **Second Denominator** (text): e.g. 8
- **Missing Term** (select)
- **Decimal Places** (number)

## When to use

- Scaling recipes or adjusting ingredient quantities based on different serving sizes.
- Resizing images, videos, or geometric shapes while maintaining the original aspect ratio.
- Solving math homework problems involving cross multiplication and equivalent fractions.

## How it works

- Enter the three known values into their respective numerator and denominator fields.
- Select which term is missing (e.g., Second Denominator) from the dropdown menu.
- Adjust the decimal places setting if you need a specific level of precision for the result.
- The calculator applies cross multiplication to find the exact value of the missing term and displays the completed equation.

## Use cases

- Calculating unit prices or comparing costs for different quantities of a product.
- Converting measurements, such as finding real-world distances from a scaled map.
- Adjusting medication dosages based on patient weight in healthcare or veterinary settings.

## Frequently asked questions

### What is a proportion equation?

A proportion equation states that two ratios or fractions are equal, typically written in the format a/b = c/d.

### How does the calculator find the missing value?

It uses cross multiplication. For example, if a/b = c/d and 'd' is missing, it calculates the result using the formula d = (b * c) / a.

### Can I use decimals as inputs?

Yes, you can input decimal numbers into the numerator and denominator fields to solve more complex proportions.

### What does the decimal places setting do?

It rounds the calculated missing term to your specified number of decimal places, allowing you to choose anywhere from 0 up to 12 decimal places.

### Is this the same as the rule of three?

Yes, solving for a missing term in a proportion equation is commonly known as the rule of three in mathematics.

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