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Home Page > Math > Basic Math Operations

Ratio Calculator

Solve proportions, simplify ratios to lowest terms, scale ratios up or down, and generate equivalent ratios. Free online ratio calculator with step-by-step solutions and visual ratio bars.

Free to useNo sign-up requiredInstant Results
Ratio CalculatorTry it now — free ▼
Group both sides equally to simplify: 12 : 18 = 2 : 3

Enter a ratio like 12:18 to simplify it, scale it, or list equivalent ratios, or solve a proportion with one value missing, with the steps.

⚡ Quick Examples:
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Leave one field empty to solve for it, or fill all four to verify the proportion.

Embed Ratio Calculator Widget

About Ratio Calculator

The Ratio Calculator is a comprehensive tool for working with ratios and proportions. Whether you need to solve for a missing value in a proportion, simplify a ratio to its lowest terms, scale a ratio by a factor, or generate a table of equivalent ratios, this calculator handles it all with visual ratio bars and step-by-step solutions.

What is a Ratio?

A ratio is a comparison of two or more quantities that shows their relative sizes. Written as a:b (read "a to b"), it tells you how much of one thing there is compared to another. For example, if a recipe calls for flour and sugar in a 3:1 ratio, you use 3 parts flour for every 1 part sugar.

Ratios can involve more than two quantities. A ratio of 2:3:5 means the first quantity is 2 parts, the second is 3 parts, and the third is 5 parts out of a total of 10 parts.

Key Ratio Formulas

Cross Multiplication (Proportion Solving)
If \(\frac{a}{b} = \frac{c}{d}\), then a × d = b × c
Simplifying a Ratio
a:b → \(\frac{a}{\gcd(a,b)}\) : \(\frac{b}{\gcd(a,b)}\)

How to Use This Calculator

  1. Select an operation mode: Choose from Solve Proportion, Simplify, Scale, or Equivalents using the tabs at the top.
  2. Enter your values: For Solve, enter three values and leave one blank. For Simplify, enter a ratio like 12:8. For Scale, enter a ratio and a multiplier. For Equivalents, enter a ratio and the number of equivalents to generate.
  3. Click Calculate: Press the Calculate button to process your input.
  4. Review results: View the answer with animated visual ratio bars showing proportions, step-by-step solution breakdown, and simplified forms.

Types of Ratio Problems

Solving Proportions

A proportion is an equation stating two ratios are equal: a:b = c:d. If one value is unknown, cross multiplication solves it. For example, if 2:3 = x:9, then 3x = 18, so x = 6.

Simplifying Ratios

To simplify a ratio, divide all parts by their greatest common divisor (GCD). For example, 12:8 has GCD = 4, so it simplifies to 3:2. This works for multi-part ratios too: 10:15:25 has GCD = 5, simplifying to 2:3:5.

Scaling Ratios

Scaling a ratio means multiplying all parts by the same factor. If a recipe for 4 servings uses a 2:1 flour-to-butter ratio and you need 12 servings (factor of 3), the scaled ratio is 6:3.

Equivalent Ratios

Equivalent ratios express the same relationship with different numbers. The ratios 1:2, 2:4, 3:6, and 4:8 are all equivalent because they all simplify to 1:2.

Real-World Applications of Ratios

FieldApplicationExample
CookingRecipe scalingFlour to sugar = 3:1
MapsScale representation1:50,000 (1 cm = 500 m)
FinanceDebt-to-income ratioMonthly debt:income = 1:3
ScienceMixing solutionsAcid:water = 1:9
ArchitectureScale modelsModel:actual = 1:100
PhotographyAspect ratioWidth:height = 16:9

Frequently Asked Questions

What is a ratio?

A ratio is a comparison of two or more quantities that shows their relative sizes. It is written as a:b (or a:b:c for three quantities) and indicates how many times one value contains or is contained within the other. For example, 3:2 means for every 3 units of the first quantity, there are 2 units of the second.

How do you solve a proportion?

To solve a proportion a/b = c/d with one unknown, use cross multiplication: a times d = b times c. Then isolate the unknown variable. For example, to solve 2/3 = x/9, cross multiply to get 3x = 18, so x = 6.

What does it mean to simplify a ratio?

Simplifying a ratio means reducing it to its smallest whole number form by dividing all parts by their greatest common divisor (GCD). For example, 12:8 simplifies to 3:2 because the GCD of 12 and 8 is 4, and dividing both by 4 gives 3:2.

How do you find equivalent ratios?

To find equivalent ratios, multiply or divide all parts of the ratio by the same non-zero number. For example, equivalent ratios of 2:3 include 4:6, 6:9, 8:12, and so on. All equivalent ratios represent the same proportion.

What is the difference between a ratio and a proportion?

A ratio compares two or more quantities (e.g., 3:4), while a proportion is an equation stating that two ratios are equal (e.g., 3:4 = 6:8). A proportion always involves two ratios connected by an equals sign.

Common Ratios

16:94:321:93:25:41.85:12.35:116:109:161:12:310:166:48:512:920:15

Reference this content, page, or tool as:

"Ratio Calculator" at https://MiniWebtool.com/ratio-calculator/ from MiniWebtool, https://MiniWebtool.com/

by miniwebtool team. Updated: Mar 20, 2026

Developer API available: Run this tool from your app, automation, or agent with one JSON HTTP request. View API docs

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