What is the difference between a ratio and a fraction?

A fraction represents part of a whole. A ratio compares two quantities. Every fraction can be expressed as a ratio, but not every ratio is a fraction.

How do I simplify a ratio?

Divide both terms by their Greatest Common Divisor (GCD). For example, 12:16 divided by GCD(12,16)=4 simplifies to 3:4.

Can a ratio have decimal terms?

Yes. This calculator accepts decimal values. Results are shown to up to 6 significant figures and also in simplified form.

What are the presets for?

Five presets load example values for Recipe, Blueprint, Map, Screen ratio, and Finance use cases, demonstrating common real-world applications.

Math

Ratio calculator

Solve equivalent ratios (A:B = C:D), scale a ratio up or down by a factor, and see the result simplified to its lowest terms. Features a visual proportional bar, step-by-step working, and five real-world presets for recipes, blueprints, maps, screen ratios, and finance.

3-mode tab strip A:B = C:D solver Scale up & down GCD simplification Visual ratio bar 5 real-world presets

Ratio Calculator

Solve · Scale · Simplify

Quick presets

Leave exactly one blank — it will be solved automatically.

Factor

Result

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Proportional view

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Simplified

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As decimal

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GCD

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Step-by-Step Working

Results rounded to 6 significant figures.

What Is a Ratio?

A ratio expresses how two quantities relate to each other. Written as A:B or A/B, it tells you for every A units of one thing, there are B units of another. Ratios are dimensionless — 3:4 remains 3:4 whether you're measuring cups, metres, or pixels — which makes them universally applicable.

Ratios can always be simplified by dividing both terms by their Greatest Common Divisor (GCD). For example, 6:9 simplifies to 2:3 because GCD(6,9) = 3. Equivalent ratios are simply scaled versions of the same simplified form.

How to Use Each Mode

Solve A:B = C:D

Enter any three of the four values and leave one blank. The missing value is found by cross-multiplication: A × D = B × C.

e.g. 3:4 = ?:8 → 3 × 8 / 4 = 6

Scale Up (Enlarge)

Multiply both terms of A:B by a scale factor to produce a proportionally larger ratio.

e.g. 3:4 × 5 = 15:20 (simplifies to 3:4)

Scale Down (Shrink)

Divide both terms of A:B by a scale factor to produce a proportionally smaller ratio.

e.g. 15:20 ÷ 5 = 3:4

GCD Simplification Explained

Every ratio can be reduced to its simplest form by dividing both terms by their GCD. The GCD is the largest integer that divides both numbers without a remainder. For example:

Original ratio	GCD	Simplified	Decimal
12:16	4	3:4	0.75
6:9	3	2:3	0.667
100:25	25	4:1	4
7:14	7	1:2	0.5
15:20	5	3:4	0.75

Real-World Applications

RecipesScale ingredient quantities proportionally when cooking for more or fewer people.

BlueprintsConvert between scale drawing dimensions and real-world measurements accurately.

MapsUse a map scale to find actual distances from measured map lengths.

Screen RatiosResize images and videos while preserving aspect ratios like 16:9 or 4:3.

FinanceCompare financial ratios like price-to-earnings, debt-to-equity, and current ratios.

ChemistryMix solutions in the correct proportions for experiments or industrial processes.

Frequently Asked Questions

A fraction represents a part of a whole (e.g. 3/4 means 3 out of 4). A ratio compares two quantities that may or may not add up to a whole (e.g. 3:4 means for every 3 of A there are 4 of B). Every fraction can be expressed as a ratio, but not every ratio is a fraction.

Divide both terms of the ratio by their Greatest Common Divisor (GCD). Use the Euclidean algorithm to find the GCD: divide the larger number by the smaller, then replace the larger with the smaller and the smaller with the remainder, repeating until the remainder is 0. The last non-zero remainder is the GCD.

Yes. This calculator accepts decimal values for A, B, C, and D. For example, 1.5:2 is a valid ratio. Results are always shown to up to 6 significant figures and also in simplified integer form where possible.

Two ratios are equivalent if they simplify to the same value. For example, 2:3, 4:6, and 6:9 are all equivalent because they all simplify to 2:3. Multiplying or dividing both terms by the same non-zero number produces an equivalent ratio.

If all four values are entered, the calculator checks whether the two ratios are equivalent (A:B = C:D) and reports whether they form a valid proportion. It also shows both simplified forms so you can compare them directly.

Five presets demonstrate common use cases: Recipe (2:3 flour-to-water), Blueprint 1:50 scale, Map 1:25000, Screen 16:9, and Finance 3:1 (debt-to-equity). Clicking a preset fills the A and B fields and selects the appropriate mode for instant calculation.

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