Free — no login required

Free Ratio Generator &
Ratio Calculator

Solve proportions, simplify ratios, compare multiple ratios, convert to fractions & percentages, and scale aspect ratios — all free, all instant.

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Ratio SolverRatio FinderAspect Ratio3-Ratio Calc% to RatioGear RatioRatio ScalerImage Ratio
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Tool 01

Ratio Solver

Enter any 3 values to solve for the 4th. A : B = C : D

Features

Everything you need for ratios.

Real-time results

Results update instantly as you type. No page reloads, no waiting.

Visual charts

Bar charts, donut charts and aspect ratio previews make ratios intuitive.

Dark mode

Toggle light/dark themes. Automatically respects your system preference.

Mobile friendly

Fully responsive. Works perfectly on phones, tablets and desktops.

No login required

100% free. All calculations happen locally in your browser. No data collected.

Copy results

One-click copy to clipboard. Share your ratio calculations easily.

Learn

What is a Ratio?

A ratio is a mathematical comparison between two or more quantities, showing how many times one value contains or is contained within another. Ratios are expressed as A:Bor A/Band are used everywhere — from cooking recipes and financial analysis to screen dimensions and medical measurements.

Part-to-Part

Compares one part to another. A recipe with 2 cups flour to 1 cup sugar is 2:1.

Part-to-Whole

Compares a part to the total. In a class of 30 with 12 girls, the girls-to-total ratio is 2:5.

Aspect Ratios

Width-to-height relationship. Common: 16:9 widescreen, 4:3 standard, 1:1 square.

Guide

How to calculate ratios.

Follow these four steps to solve any ratio or proportion problem:

1

Set up the proportion

Write the two ratios as a proportion: A:B = C:D. Identify which value is unknown.

2

Cross multiply

Multiply the means and extremes: A × D = B × C. This creates a simple equation.

3

Solve for the unknown

Divide both sides by the coefficient of the unknown variable to isolate and find its value.

4

Simplify if needed

Divide both parts by their GCD (Greatest Common Divisor) to reduce to simplest form.

Example

If 3:4 = 6:?, find the missing value.

Cross multiply: 3 × ? = 4 × 6

3 × ? = 24 → ? = 24 ÷ 3

? = 8 ✓

Reference

Common aspect ratios.

Quick reference for screen sizes, photography, and video formats.

RatioDecimalCommon UseResolution
1:11.00Square — Instagram posts, profile pictures1080×1080
4:31.33Standard TV, iPad, older monitors1024×768
3:21.50DSLR photography, 35mm film1920×1280
16:101.60MacBook displays, some monitors1920×1200
16:91.78Widescreen TV, YouTube, 1080p/4K1920×1080
21:92.33Ultra-wide monitors, cinematic2560×1080
32:93.56Super ultra-wide monitors5120×1440
9:160.56Vertical video — TikTok, Reels, Shorts1080×1920
2:30.67Portrait photography, Pinterest pins1000×1500
5:41.25Large format photography, some prints1280×1024
FAQ

Frequently asked questions.

Everything you need to know about ratios, our ratio generator, and how to use our tools.

What is a ratio generator?

A ratio generator is an online tool that automatically creates, solves, simplifies, compares, and converts ratios between two or more quantities. Our free ratio generator handles everything from basic A:B ratios to complex proportions, aspect ratios, and percentage-to-ratio conversions.

What is a ratio and how does it work?

A ratio is a mathematical comparison between two or more quantities. It shows how many times one number contains another. For example, 3:2 means for every 3 of one thing, there are 2 of another. Ratios are used in cooking, finance, engineering, medicine, and everyday life.

How do I simplify a ratio using the ratio finder?

Find the Greatest Common Divisor (GCD) of both numbers, then divide both parts by it. For example, 12:8 → GCD is 4 → 12÷4 : 8÷4 = 3:2. Our Ratio Simplifier tool does this automatically in real time.

How do I use the 3 ratio calculator?

Enter three known values in the A:B = C:D form and leave one field blank. The ratio solver will automatically calculate the missing value using cross-multiplication. This works for any proportion or 3-term ratio problem.

What is an aspect ratio calculator?

An aspect ratio calculator finds the width-to-height relationship of images, screens, or any rectangular object. Common aspect ratios include 16:9 (widescreen), 4:3 (standard), 1:1 (square), and 21:9 (ultrawide). Use our Ratio Scaler to resize while preserving the aspect ratio.

How do I convert percentage to ratio?

To convert a percentage to a ratio, divide the percentage by 100, then simplify. For example, 75% = 75/100 = 3:4. Our Ratio Converter tool handles percentage-to-ratio conversion automatically — just enter the ratio and see the percentage instantly.

Can this tool work as a gear ratio calculator?

Yes! Use the Ratio Solver (A:B = C:D) to calculate gear ratios. Enter the number of teeth on the drive gear and driven gear to find the speed or torque ratio. The Ratio Scaler is also useful for calculating scaled gear ratios.

Is this ratio calculator free to use?

Yes! All tools on RatioCalculate.com — including the ratio generator, ratio finder, ratio solver, aspect ratio calculator, and ratio comparator — are completely free with no login required. All calculations happen locally in your browser.

The Best Free Ratio Generator & Ratio Calculator Online

Welcome to RatioCalculate.com — the most comprehensive free ratio generator and ratio calculator available online. Whether you need to solve a proportion, find a missing value, simplify a complex ratio, or convert between different representations, our suite of five tools handles it all instantly — with no login, no ads, and no cost.

What Is a Ratio Generator?

A ratio generator is a digital tool that creates, calculates, and analyzes ratios between two or more quantities. Unlike a basic calculator, a dedicated ratio generator understands proportional relationships — it can solve for a missing value in A:B = C:D, simplify 24:36 to 2:3, compare three different ratios side by side, or scale a ratio by any factor. Our ratio generator covers all of these use cases in one clean, modern interface.

Five Powerful Tools in One Ratio Calculator

Our ratio calculator is not just one tool — it is a complete toolkit for anyone who works with ratios:

  • Ratio Solver (Ratio Finder): The most powerful tool in the suite. Enter any three values of A:B = C:D and the ratio finder instantly solves for the missing fourth. This is the go-to 3 ratio calculator for proportional reasoning, cross-multiplication, and missing-value problems.
  • Ratio Simplifier: Paste any ratio — even one with large numbers or decimals — and get the simplified form using the Greatest Common Divisor (GCD). Includes a step-by-step breakdown so you can see exactly how to do ratios manually.
  • Ratio Comparator: Compare up to three ratios simultaneously with color-coded animated bar charts. Instantly see which ratio is larger and whether any are equivalent.
  • Ratio Converter: Functions as a percentage to ratio calculator in reverse. Enter any ratio and get the equivalent fraction, decimal, percentage, and parts-of-whole breakdown. An animated donut chart makes the conversion visually clear.
  • Ratio Scaler: Scale any ratio by a custom factor using a live slider. Perfect as an aspect ratio calculator or ratio image calculator — enter your image width and height, then scale to any target size while preserving the ratio.

Real-World Uses for Our Ratio Tools

Ratios appear in virtually every field. Here is how different users rely on our ratio generator daily:

  • Photography & Design: Use the aspect ratio calculator to resize images without distortion. Common aspect ratios like 16:9, 4:3, and 3:2 are instantly accessible.
  • Engineering & Mechanics: Our ratio solver doubles as a gear ratio calculator. Enter the number of teeth on two gears to find the speed or torque ratio and scale accordingly.
  • Health & Fitness: Calculate your waist-to-height ratio by entering your waist and height measurements. Our ratio simplifier shows you the ratio, decimal, and percentage in seconds.
  • Medicine: The PF ratio calculator (PaO₂/FiO₂ ratio) is commonly used in pulmonary medicine to assess lung function. Enter PaO₂ and FiO₂ values to calculate the ratio instantly.
  • Cooking & Baking: Scale recipes up or down using the Ratio Scaler. Enter the original ingredient ratio and apply your chosen scale factor to get perfect measurements every time.
  • Finance & Business: Financial ratios like debt-to-equity, current ratio, and price-to-earnings are all just ratios. Use our ratio solver to solve, compare, or simplify any financial metric.

How to Do Ratios — A Quick Guide

If you have ever wondered how to do ratios, the key steps are: (1) identify the two quantities being compared; (2) write them as A:B; (3) simplify by dividing both by their GCD; (4) use cross-multiplication to solve for unknowns in a proportion. Our tools handle all four steps automatically — but the step-by-step display in the Simplifier and Solver means you can follow the math and learn at the same time.

Why Choose RatioCalculate.com?

Unlike generic calculators buried in cluttered websites, our ratio generator is purpose-built for ratio work. It is fast (results appear as you type), accurate (using precise GCD algorithms), visual (animated charts make ratios tangible), and completely free — no account, no paywall, no tracking. Whether you are a student learning how to do ratios for the first time, a professional needing a quick gear ratio calculation, or a designer checking an image aspect ratio, RatioCalculate.com has the right tool for you.