Ratio Calculator

Free Online Proportion Calculator

Ratio Calculator is a free online tool for easily calculating unknown values in proportion equations (X : A = B : C). Perfect for recipe adjustments, map scale calculations, aspect ratio conversions, and more in daily life and work. Simply enter the values and get instant results through automatic cross multiplication.

How to Use - Easy Calculation in 3 Steps

Using the Ratio Calculator is very simple:

Step 1: Select Calculation Type
Choose whether you want to solve for X or solve for Y.
Step 2: Enter Known Values
Enter the three known numbers in the proportion equation.
Step 3: View Result
The unknown value is calculated in real-time as you type and displayed in the result field.

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Ratio Calculator Tool

Simplified Ratio

For proportion: Enter one value to find the other. If a:b = value:?, enter value in A. If a:b = ?:value, enter value in B.

Proportion Calculation

Percentage Conversion

Decimal Conversion

For scale: Enter the multiplication factor in value A to scale the entire ratio.

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Scaled Ratio

Practical Use Cases for Ratio Calculation

Ratio calculation is used in various situations in daily life and business:

Cooking & Recipes

When adjusting recipe quantities for different serving sizes, ratio calculations are essential. For example, if a recipe calls for ingredients in a 2:3 ratio and you need to scale it up, a ratio calculator quickly determines the correct amounts.

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What is a Ratio? Understanding the Basics

A ratio is a mathematical expression that compares two quantities by division. It shows the relative sizes of two or more values. Ratios are written as A:B (read as "A to B") or as a fraction A/B.

Simplifying Ratios

Simplifying a ratio means reducing it to its lowest terms by dividing both numbers by their greatest common divisor (GCD). This makes the ratio easier to understand and work with. For example, 8:12 simplifies to 2:3 because both 8 and 12 are divisible by 4.

Simplification Example

Original Ratio: 24:36
GCD of 24 and 36 = 12
Simplified Ratio: 2:3 (24÷12 : 36÷12)

Proportion and Cross Multiplication

A proportion is an equation stating that two ratios are equal: A:B = C:D. To find a missing value, use cross multiplication: A×D = B×C. For example, if 3:5 = X:15, then X = (3×15)/5 = 9.

Proportion Example

If 2:3 = X:12, then X = (2×12)/3 = 8
Verification: 2:3 = 8:12 ✓

Frequently Asked Questions (FAQ)

In what situations is ratio calculation used?

It's used in a wide range of situations from daily life to business, including recipe adjustments, map scale calculations, exchange rate conversions, aspect ratio conversions, and scaling architectural drawings.

What is cross multiplication?

In the proportion A : B = C : D, it's a method of finding unknown values using the relationship B × C = A × D. For example, for X : 9 = 4 : 3, calculate X = (9 × 4) ÷ 3 = 12.

Can I calculate with decimals and fractions?

Yes, you can. This tool supports decimal numbers and displays accurate calculation results.

What happens if I divide by zero?

Since dividing by zero is mathematically impossible, an error message is displayed. Please enter values so that the denominator in the calculation is not zero.

What's the difference between proportion and inverse proportion?

In proportion, 'if one doubles, the other doubles'; in inverse proportion, 'if one doubles, the other halves'. This tool is for proportion calculation only.

What if the calculation result doesn't display?

You need to enter all three known values. Also, make sure the denominator value is not zero.

Can I copy the calculation result?

Yes, you can select and copy the number displayed in the result field. You can paste it directly into other applications.

Can I calculate with negative numbers?

Theoretically possible, but this tool assumes positive numbers from 0 and above. Ratio calculation is typically used for positive quantities like length, weight, and time.