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Math & Numbers Runs in browser Updated 30 Mar 2026

Ratio Calculator

Simplify ratios, scale to a target value, compare two ratios for equivalence, and convert between ratios, fractions, and percentages. Aspect ratio presets included.

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Enter a ratio to simplify.

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Percentages

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Formulae

Simplify A:B = divide both by GCD(A, B)

Scale A:B to A'=T → B' = T × B / A

A:B = C:D iff A × D = B × C (cross-multiplication)

Golden ratio φ = (1 + √5) / 2 ≈ 1.618034
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How to use Ratio Calculator

  1. Choose a mode

    Select Simplify, Scale, Compare, Convert, or Aspect Ratio from the tabs.

  2. Enter your ratio parts

    Type the numbers that form the ratio. For three-way ratios, fill in all three fields.

  3. Read the result

    The simplified ratio, missing value, equivalence check, or converted form appears instantly.

  4. Use aspect ratio presets

    In Aspect Ratio mode, select a preset like 16:9 or 4:3 and enter one dimension to calculate the other.

Ratio Calculator FAQ

How do I simplify a ratio?
Divide both parts by their greatest common divisor (GCD). Example: 24:36 — GCD is 12 — simplifies to 2:3.

How do I scale a ratio to a target?
Multiply both parts of the ratio by the same factor. Example: 3:5 scaled so the first part is 12 → multiply by 4 → 12:20.

How do I check if two ratios are equivalent?
Use cross-multiplication: a:b = c:d if a × d = b × c. Example: 2:3 and 8:12 → 2×12 = 24, 3×8 = 24 → equivalent.

What is the golden ratio?
The golden ratio φ ≈ 1.6180339887. A rectangle has golden ratio proportions when the ratio of its longer to shorter side equals φ. Found in art, architecture, and nature.

What aspect ratios are available?
Presets include 16:9 (widescreen HD), 4:3 (standard), 1:1 (square), 21:9 (ultrawide), 9:16 (portrait/mobile), 3:2 (DSLR), and 5:4.

Can I calculate a three-way ratio?
Yes. Enter all three parts (a:b:c) in the simplify or scale fields. Useful for ingredient proportions, profit sharing, and mixing problems.

How do I convert a ratio to a percentage?
Treat the ratio a:b as the fraction a/(a+b) for the first part's share. Multiply by 100 for the percentage. The convert mode does this automatically.

What is the difference between a ratio and a fraction?
A ratio a:b compares two quantities. The equivalent fraction is a/b (or a/(a+b) for the share). Both represent proportional relationships.

Can I use this for recipes?
Yes. Enter the original ingredient ratio and scale it to your target quantity using the Scale mode.

Is any data sent to a server?
No. All calculations run entirely in your browser. Nothing is uploaded or stored.

Background

Work with ratios effortlessly across four modes. Simplify reduces any ratio to its lowest terms by dividing by the GCD. Scale mode lets you find a missing value when scaling a ratio to a target — useful for recipes, maps, and blueprints. Compare mode uses cross-multiplication to test whether two ratios are equivalent. Convert mode transforms a ratio into a fraction, decimal, and percentage simultaneously. Aspect ratio mode includes common presets (16:9, 4:3, 1:1, 21:9, 9:16) for display and video work, plus a golden ratio calculator. Three-way ratio support handles a:b:c distributions for ingredient splitting, profit sharing, and similar problems. All processing runs in your browser with no data uploaded or account required.

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