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Ratio Calculator

Scale a ratio A:B by any factor and instantly see the equivalent and simplified ratio. Paste in two numbers, pick a multiplier, and this free ratio calculator does the math for you — with no signup and nothing uploaded.

Scale by (factor)

8 : 12

What is a ratio calculator?

A ratio calculator is a tool that takes two (or more) numbers — like 4 and 6 — and expresses them as a ratio A:B, scales that ratio by a factor you choose, and simplifies the result to its lowest terms. Ratios are one of the oldest ways to compare two quantities: for every A units there are B units, so 2:3 means two parts of one thing for every three of another.

Behind the scenes, scaling multiplies both parts of the ratio by your factor, while simplifying divides both parts by their greatest common divisor (GCD) until no smaller whole numbers remain. So 4:6 scaled by 2 becomes 8:12, and simplified it drops back to 2:3. The same idea powers ratio-to-percentage conversion, equivalent ratios, and the proportions used in cooking, mixing and finance.

This calculator runs entirely in your browser, so you get instant results with a private, offline computation.

How to use the ratio calculator

Type the first number into the A field and the second into the B field.
Enter the factor you want to scale the ratio by — 2, 3, 0.5, or any number.
Click Calculate to see the scaled ratio, the working-out and the simplified form.

Example

Enter A = 4, B = 6 and a factor of 2. The calculator shows 8 : 12, explains that it comes from (4 × 2) : (6 × 2), and notes the simplified equivalent 2 : 3. Choose a factor of 3 and the same ratio becomes 12 : 18, which still simplifies to 2 : 3.

Who is this Ratio Calculator for?

Anyone who needs to compare two quantities or keep a proportion steady — students, teachers, college learners and working professionals all reach for the same simple idea.

Students: solve ratio and proportion homework, simplify a ratio to its lowest terms and check that two amounts really are in the same relationship.
Teachers: build clean worked examples, show how scaling multiplies both parts and demonstrate simplifying by the greatest common factor.
College students: handle ratios and proportions in maths, chemistry or statistics assignments where A:B appears as a shorthand for a relationship.
Professionals: keep mixes consistent in recipes, recipes for products, or designs — from a cake mix to a paint ratio or a screen aspect ratio.

Common ratios at a glance

This table shows which ratios are already in lowest terms and which simplify down. The calculator derives these instantly — here is the pattern behind common formats.

Ratio	Simplified	HCF	Typical use
16:9	16:9	1	Widescreen TV and monitor
4:3	4:3	1	Classic video and photo
3:2	3:2	1	Photography frames
1920:1080	16:9	120	Full HD screen pixels
4:6	2:3	2	Doubling a recipe mix
14:21	2:3	7	Simplify by 7 example

For a 2:3 ratio the first part is 2/(2+3) = 40% of the total, which is the basis for turning any ratio into a percentage.

Common use cases

Recipes and mixes — doubling or halving ingredients while keeping the mix consistent.
Scaling a recipe, a drawing, a model or a plan to a new size.
Comparing two numbers such as a grade ratio, a win–loss record or an ingredient mix.
Converting a ratio to a percentage or a fraction for reports and spreadsheets.

Pro tips

To simplify a ratio on its own, just set the factor to 1 and the calculator will show the lowest terms.
Use a factor of 10, 100 or 0.1 to work with decimals like 0.5 : 0.75 without the arithmetic.
Keep both inputs as whole numbers where possible — the simplified ratio reads more naturally.
Use the same tool in reverse: enter the desired ratio and scale up to reach a target quantity.

FAQ

How do I scale a ratio?

Multiply both parts by the factor. The ratio 4:6 scaled by 2 becomes 8:12 — every part is multiplied by the same number, so the relationship stays the same.

How do I simplify a ratio?

Divide both parts by their greatest common divisor. 4:6 divides by 2 to give 2:3, which is the simplest whole-number form.

What does A:B mean?

It compares two quantities: for every A units of the first there are B units of the second. A ratio of 2:3 means two of one thing for every three of another.

How do I turn a ratio into a percentage?

Add the two parts, divide one part by the total and multiply by 100. For 2:3, the first part is 2/(2+3) = 40%.

Can I get an equivalent ratio?

Yes. Multiply both parts by the same number — 1:2, 2:4, 3:6 and 10:20 are all equivalent ratios.

What is an aspect ratio?

A ratio that compares width to height, such as 16:9 or 4:3. It is used for screens, images and videos to keep proportions correct.

Is this ratio calculator free?

Yes. It is completely free with no signup, no limits and no hidden charges.

Does it run in my browser?

Yes. Everything is calculated locally on your device — no data is uploaded or stored anywhere.

Can I use decimals in a ratio?

Yes. Enter values such as 0.5 and 1.5 and the calculator will scale and simplify them using a decimal-safe greatest common divisor.

Why simplify a ratio?

Simplified ratios are easier to read and compare. 2:3 is instantly understood, while 14:21 takes a moment to reduce mentally.