Ratio Calculator

Simplify ratios and solve proportions with cross multiplication.

  • Formula checked
  • Editorially reviewed
  • Free · no signup
  • Updated June 27, 2026

Your details

Your result

Where to go next

Next logical calculatorScientific CalculatorFull expression scientific calculator with trig, logs, roots, powers and factorials.Continue

Quick answer

What it does
Ratio Calculator simplify ratios and solve proportions with cross multiplication. It runs entirely in your browser, needs no signup, and uses standard published U.S. formulas.
When to use
Use it whenever you need a fast, reliable ratio estimate.
Inputs
  • A
  • B
  • C (optional — solve A : B = C : D)
Outputs
  • Simplified Ratio
  • Missing Value (D)
  • As a Fraction
  • As a Decimal
  • Share of Total
  • Scaled to 1
Takeaway
In one line: enter your a and b and the Ratio Calculator returns simplified ratio and missing value (d) you can compare before deciding.

Last updated · 1 min read

How to read your result

Ratio Calculator: Your result appears above. It's a fast estimate based on the inputs you entered — use it to compare options, then confirm with a professional before making a decision.

What your result means

  • The number is only as accurate as your inputs — small errors compound.
  • Compare 2–3 scenarios rather than acting on a single result.
  • Talk to a licensed professional before making a large financial or medical decision.

How does the formula work?

Simplified ratio = (A ÷ GCD) : (B ÷ GCD). Proportions solve by cross multiplication: if A : B = C : D then A·D = B·C, so D = (C × B) ÷ A.

How it works

Ratios compare two quantities without units, and proportions scale that comparison up or down. They power screen and image aspect ratios, map scales, recipe scaling, mixing paint or fuel, gear ratios and chemistry dilutions. Cross multiplication is the single most useful proportion technique in U.S. middle and high school math, and it is the exact method this calculator uses to fill in a missing fourth term.

Step-by-step guide

  1. 1Enter each input value into the calculator above.
  2. 2Review the result and any auto-generated breakdowns.
  3. 3Adjust inputs to compare scenarios.
  4. 4Copy, share, or print the results.

Example calculation

Example: A 16 : 9 screen that is 1920 px wide is 1080 px tall.

Who should use this calculator?

  • Anyone who needs a fast, transparent estimate before making a decision.
  • Professionals validating a client-facing number.
  • Students learning the underlying formula.

When should you use it?

  • Any time you need a quick sanity check.
  • When comparing several scenarios side-by-side.
  • Before making a decision that depends on this number.

What affects the result?

  • Every input value you enter
  • The formula and assumptions displayed on this page
  • Rounding — small differences in inputs compound in the result

Common mistakes to avoid

  • Entering values in the wrong units.
  • Assuming the result includes taxes or fees when it may not.
  • Using rounded inputs and expecting exact figures.

Pro tips

  • Double-check your inputs before acting on the result.
  • Run 2–3 scenarios and compare — don't rely on a single number.
  • Save or print the results so you can review them later.

Why use this calculator

  • Instant results with no signup, no tracking and no ads inside the calculator.
  • Transparent formulas — you can see exactly how the number is produced.
  • Save, share, print or embed your results anywhere.
  • Reviewed and updated regularly by our editorial team.

Limitations to keep in mind

  • Estimates only — real-world results depend on many factors we cannot see.
  • Not professional advice — consult a qualified expert before acting.
  • Assumptions are shown; changing them will change the result.

Key terms explained

Input
A value you enter into the calculator. Small differences in inputs can compound into large differences in the result.
Assumption
A fixed value the calculator uses when it isn't asked from you. Assumptions are documented in the formula section.
Estimate
A directional figure produced from your inputs and standard formulas. Always sanity-check before acting.

Before you decide

  • Double-check every input for units and typos.
  • Compare 2–3 scenarios rather than trusting one result.
  • Confirm the assumptions in the formula match your situation.
  • Consult a qualified professional before acting on any large decision.

Trust & Accuracy

Accuracy tested

Verified against standard mathematical and financial conventions. Edge cases, formula validation and manual verification completed (last reviewed June 27, 2026).

Educational use

This tool is provided for education and planning only. It is not financial, tax, legal or medical advice.

Available for

United States, Canada, United Kingdom, Australia, India, European Union.

Currency support

USD · INR · CAD · AUD · GBP · EUR

Privacy

No information entered into this calculator is stored on our servers unless you explicitly choose to save or share your calculation.

Print, share & save

Use the Save, Share, Copy, PDF, CSV and Print actions under the result panel.

Accessibility

Keyboard navigable, screen-reader friendly labels, responsive on mobile and desktop.

Learn more: How we verify formulas · How we test accuracy · Methodology · Editorial policy

Recent Updates

We continuously review and improve our calculators to keep formulas, assumptions and references accurate.

View change log (4)Show
  1. v1.3

    Added Trust & Accuracy panel and machine-readable change log.

  2. v1.2

    Added Save, Share, PDF, CSV and Print actions to results.

  3. v1.1

    Added global currency selector (USD, INR, CAD, AUD, GBP, EUR).

  4. v1.0

    Initial calculator release with verified formulas and Official Sources.

Share this Calculator

Share to any platform, embed it on your site, or scan the QR code. No sign-up required.

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Frequently Asked Questions

Related guides

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What's next?

Your next step

Most people who use this calculator explore these next. Follow the path in order for a complete plan.

  1. 1Square Root CalculatorSquare roots in decimal and simplified radical form, plus cube and fourth roots.
  2. 2Fraction SimplifierReduce any fraction to lowest terms and see the greatest common divisor.
  3. 3Image Aspect Ratio CalculatorResize images without distortion and match standard social and video ratios.
  4. 4Working Capital CalculatorWorking capital, current ratio and quick (acid-test) ratio.

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Reviewed by the CreditLoanCalculator editorial team·Last reviewed ·Editorial policy·How we verify formulas
Disclaimer: Results are estimates for informational purposes only and should not be considered financial, medical, legal, or professional advice. Always consult a qualified professional before making decisions.