Ratio Calculator

Simplify ratios to lowest terms, check equivalence with cross-multiplication, or reduce width×height to a clean aspect ratio like 16:9—all in your browser.

Runs in your browser · No data stored · No signup

A ratio calculator simplifies a:b to lowest terms using the greatest common divisor (GCD) and checks whether two ratios are equivalent by cross-multiplication (a×d = b×c)—all in your browser.

Uses the Euclidean algorithm for GCD and cross-multiplication for equivalence. Decimal display is for convenience; equivalence uses exact cross-products when possible.

Simplify 12:18

GCD = 6 → divide both terms → 2:3

Equivalent?

2:3 and 8:12 match because 2×12 = 3×8 = 24

Privacy

Runs locally in your browser—no upload

Simplify ratio

Reduce a:b to lowest terms using the greatest common divisor (GCD).

Simplify

Compare

Aspect ratio

Simplified ratio

12:182:3

Decimal (first ÷ second): 0.666667

GCD used: 6

How this result was calculated
  1. Ratio: 12 : 18
  2. GCD(12, 18) = 6
  3. Divide both terms: 12÷6 : 18÷6 = 2:3
  4. Decimal (first ÷ second): 0.666667

Press C to copy when not typing in a field.

Related calculators

Fraction Calculator

Add, multiply, and convert fractions—not just simplify ratios.

Percentage Calculator

Turn ratios into percents and parts of a whole.

By Muhammad Abdullah Rauf · Founder, EverydayTools.proUpdated 2026-05-20· Reviewed by EverydayTools Editorial Team

What is a ratio calculator?

A ratio expresses how two quantities compare, written as a:b (read “a to b”). Unlike a fraction a/b, ratios often stay in colon form for recipes, maps, betting odds, and mix ratios. Simplifying means dividing both terms by their GCD so no smaller whole-number ratio represents the same proportion—12:18 becomes 2:3 because GCD(12, 18) = 6.

To see if two ratios match without converting to decimals, cross-multiply: a:b equals c:d when a×d equals b×c. Example: 2:3 and 8:12 are equivalent because 2×12 = 24 and 3×8 = 24. This calculator runs locally in your browser; your numbers are not uploaded to EverydayTools servers.

Use the fraction calculator when you need arithmetic on fractions, or the percentage calculator when converting a ratio to a percent of a whole.

Quick answers

Concise answers for common searches — definitions, steps, and comparisons.

How do you simplify 12:18?

GCD(12, 18) = 6. Divide both terms: 12÷6 = 2, 18÷6 = 3. Simplified ratio: 2:3.

When are two ratios equivalent?

Ratios a:b and c:d are equivalent when a×d = b×c. Example: 2:3 and 8:12 because 2×12 = 3×8 = 24.

Is the ratio calculator private?

Yes. Calculations run locally in your browser; your inputs stay on your device and are not uploaded.

What is the ratio formula for simplification?

Divide both terms by GCD(a, b): simplified a:b = (a÷g):(b÷g). Equivalence: a:b = c:d when a×d = b×c.

Ratio simplification

Divide both terms by GCD; equivalence uses cross-multiplication with floating-point tolerance for decimals.

Formula

Simplified a:b = (a÷g):(b÷g) where g = GCD(a,b)
Equivalent when |a×d − b×c| < ε

Assumptions

  • Terms are numeric and b (and d when comparing) are non-zero

Limitations

  • Does not solve for an unknown term in a proportion (a:b = c:x) — set up algebra manually or use a dedicated proportion solver

How to use Ratio Calculator

  1. Enter the first ratio

    Type the two terms a and b (e.g. 12 and 18). The second term cannot be zero.

  2. Read the simplified ratio

    The tool divides both terms by the GCD and shows the reduced ratio, decimal value (a÷b), and the GCD used.

  3. Compare a second ratio (optional)

    Enable comparison and enter c:d. The calculator cross-multiplies to show equivalent or not, with the cross-products displayed.

  4. Copy or apply the result

    Use 2:3 in recipes, scale drawings, or homework checks. For fraction math (add/multiply), open the fraction calculator instead.

Ratio Calculator examples

Simplify 12:18

Input

12 : 18

Output

2 : 3 (decimal ≈ 0.667)

GCD(12, 18) = 6. Divide both terms: 12÷6 = 2, 18÷6 = 3.

Compare 2:3 and 8:12

Input

2:3 vs 8:12

Output

Equivalent

2×12 = 24 and 3×8 = 24 — cross-products match.

Non-equivalent check

Input

3:4 vs 2:3

Output

Not equivalent

3×3 = 9 but 4×2 = 8 — cross-products differ.

Who uses Ratio Calculator?

Common real-world scenarios where this tool saves time.

Recipe scaling

Reduce ingredient ratios like 6:9 to 2:3 before doubling or halving a recipe.

Map and model scales

Confirm whether two scale statements (e.g. 1:50 vs 2:100) represent the same proportion.

Classroom and homework checks

Verify simplified ratios and equivalence without manual GCD division.

Mix ratios and dilution

Normalize paint, coolant, or chemical mix ratios to lowest terms before scaling volume.

Workflow guides

Step-by-step chains that connect related tools for common tasks.

Recipe ratio then scale

  1. Simplify the ingredient ratio here (e.g. 6:9 → 2:3).
  2. Scale portions with the Fraction Calculator if you need fractional cups or batch multiplication.

Reference tables

Ratio calculator vs fraction vs percentage

Pick the right EverydayTools calculator for your task.

ToolBest for
Ratio CalculatorSimplify a:b and test if two ratios are equivalent
Fraction CalculatorAdd, subtract, multiply, or divide fractions
Percentage CalculatorConvert between percent, fraction, and decimal parts of a whole

Common mistakes to avoid

Swapping terms thinking order does not matter

2:3 and 3:2 are different ratios. Keep the same order as your problem statement (e.g. flour:sugar).

Comparing by decimal rounding only

Use cross-multiplication for exact equivalence; decimals can hide small differences.

Advertisement

Frequently Asked Questions

How do you simplify a ratio?

Divide both terms by their greatest common divisor (GCD). Example: 12:18 → GCD is 6 → 12÷6 = 2 and 18÷6 = 3, so the simplified ratio is 2:3.

How do you know if two ratios are equal?

Cross-multiply: a:b equals c:d when a×d = b×c. Example: 2:3 and 8:12 are equivalent because 2×12 = 24 and 3×8 = 24.

What is the difference between a ratio and a fraction?

A ratio a:b compares two quantities and is often left in colon form. A fraction a/b usually means “a parts of b equal parts of a whole.” The same numbers can look different in context—use this tool for simplifying ratios; use the fraction calculator for adding or multiplying fractions.

Can ratios include decimals?

Yes. Enter decimal terms; the calculator still finds a GCD on rounded integers where applicable and shows the decimal value a÷b for comparison.

Does the ratio calculator upload my numbers?

No. All simplification and comparison runs locally in your browser. Nothing is sent to EverydayTools servers.

Is this ratio calculator free?

Yes—free with no signup, no usage limits, and no ads required to see your result.

Can I simplify aspect ratios like 1920×1080?

Yes. Use Aspect mode (or enter width and height as the two terms). 1920:1080 simplifies to 16:9—the same GCD method as any other ratio.

Privacy, accuracy, and trust

Privacy

Ratio terms and comparison inputs stay in your browser. Results are computed with JavaScript on your device—nothing is uploaded to EverydayTools.

Accuracy

Uses the Euclidean algorithm for GCD and cross-multiplication for equivalence. Decimal display is for convenience; equivalence uses exact cross-products when possible.

For financial, medical, or safety-critical mix ratios, verify with domain-specific guidelines.

Advertisement

Reviewed by EverydayTools Editorial Team on 2026-05-20.

Related tools

Same workflow or intent — pick the next step without leaving the site.

Fraction Calculator

Add, subtract, multiply, divide, and simplify fractions with clear step-by-step work—see mixed numbers, decimals, and reduced forms instantly.

Combination Calculator — nCr (n Choose r)

Calculate combinations nCr = n!/(r!(n−r)!) for unordered selections. No upload: runs locally in your browser. Free, instant nCr results.

Exponent Calculator

Calculate powers like a^b, negative exponents, and fractional exponents with clear results and quick examples like 2^3 = 8. Runs locally in your browser when supported—no upload required for normal use.

Factorial Calculator — n! (n Factorial)

Calculate factorial n! for 0 ≤ n ≤ 500 with exact big-integer results. No upload—runs locally in your browser. Free, instant n! for combinatorics.

GCF Calculator

Find the greatest common factor of two or more integers using the Euclidean algorithm and factor-method explanations. Runs locally in your browser when supported—no upload required for normal use.

LCM Calculator

Calculate the least common multiple of two or more integers with formula-based steps and prime factorization guidance. Runs locally in your browser when supported—no upload required for normal use.

Popular in this category

Frequently opened tools from the same category.

BMI Calculator

Calculate BMI from height and weight using metric or imperial units. See BMI category ranges and use it as a quick screening estimate. Runs locally in your browser when supported—no upload required for normal use.

Calorie Calculator

Estimate daily calories using the Mifflin-St Jeor BMR formula and TDEE activity multipliers for maintenance, weight loss, or weight gain. Runs locally in your browser when supported—no upload required for normal use.

Tip Calculator

Free tip calculator — find tip amount, bill + tip total, and per-person share. Presets for common percentages (10%, 15%, 20%), custom %, and equal split. Runs in your browser. No signup.

Percentage Calculator

What is 20% of 500? Percent increase, decrease, difference, reverse %, markup & margin—runs locally in your browser, no upload. Copy results or share a link.

People also use

Cross-category tools others open in the same session.

JSON Formatter

Free JSON formatter — paste minified or messy JSON and instantly get beautified, indented output with syntax highlighting and error detection. Browser-based, no server upload. Runs locally in your browser when supported—no upload required for normal use.

Image Compressor — Compress JPG, PNG & WebP Online

Compress JPG, PNG & WebP in your browser—up to 80% smaller, batch 25 files, 50/100/200 KB presets. Files stay on your device. No signup.

Merge PDF

Free PDF merger — combine multiple PDF files into one document. Drag to reorder files, preview pages, and download the merged PDF instantly. No signup, fully browser-based. Runs locally in your browser when supported—no upload required for normal use.

Word Counter

Instantly count words, characters, sentences, paragraphs, and reading time. Great for essays, articles, and SEO writing. No signup — works as you type. Runs locally in your browser when supported—no upload required for normal use.

Continue learning

Guides and walkthroughs that reference this tool.

Free Online Calculator Suite — 10 Essential Calculators for Everyday Math

10 free browser calculators: BMI, tip, discount, overtime, GPA, compound interest. No upload—runs locally. No signup.

BMI Calculators Compared — Metric, Imperial & Categories

2026 roundup of BMI calculators—EverydayTools, CDC, NIH, Healthline, and Calculator.net compared on accuracy, privacy, units, and clinical context.

Explore categories

Browse full tool collections by topic.

Calculator ToolsUnit Converters