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Ratio Calculator

Simplify a ratio like 8:12 to its lowest terms, see it as a decimal and a percentage, and solve equivalent ratios — all instantly in your browser.

Simplified ratio
2 : 3

As a decimal: 0.6667 · As a percentage: 66.67%

Quick answer

To simplify a ratio, divide both numbers by their greatest common divisor (GCD). For 8:12 the GCD is 4, so 8:12 reduces to 2:3. This calculator does that automatically, also showing the ratio as a decimal (0.667) and a percentage (66.7%), and it can solve an equivalent ratio such as 2:3 = 10:? → 15.

Formula & method

The tool divides both terms by their greatest common divisor to reduce the ratio to lowest terms. Decimal inputs are first scaled to whole numbers. The decimal form is A ÷ B and the percentage is that decimal × 100. To solve an equivalent ratio A:B = C:x, it cross-multiplies: x = B × C ÷ A.

Examples

Example 1: Simplify 8:12
Input
A = 8, B = 12
Result
2 : 3
Why
Both share a GCD of 4, so 8÷4 : 12÷4 = 2:3.
Example 2: Simplify 18:24
Input
A = 18, B = 24
Result
3 : 4
Why
The GCD is 6, giving 3:4 (decimal 0.75, 75%).
Example 3: Solve an equivalent ratio
Input
2 : 3 = 10 : ?
Result
15
Why
x = 3 × 10 ÷ 2 = 15, so 2:3 = 10:15.

When to use this tool

  • Scaling a recipe, mixture, or paint/chemical blend up or down.
  • Reducing an aspect ratio or odds to their simplest form.
  • Checking whether two ratios are equivalent.

Common mistakes

  • Forgetting to divide BOTH terms by the same number — a ratio only stays equivalent if you scale both sides equally.
  • Reading 2:3 as 'two thirds' — the fraction of the whole that the first part represents is 2/(2+3) = 2/5, not 2/3.
  • Mixing up the order: 8:12 and 12:8 are different ratios that reduce to 2:3 and 3:2.

Frequently asked questions

How do I simplify a ratio?

Divide both terms by their greatest common divisor (GCD). For example, 8 and 12 share a GCD of 4, so 8:12 becomes 2:3. This tool finds the GCD and reduces it for you.

Can it handle decimal ratios?

Yes. Decimals are scaled to whole numbers before simplifying, so 1.5:3 reduces correctly to 1:2.

What is the ratio as a percentage?

It is the decimal value (first term ÷ second term) multiplied by 100. For 2:3 that is 0.667 × 100 ≈ 66.7%.

How do I solve A:B = C:x?

Cross-multiply: x = B × C ÷ A. Enter the equivalent-ratio box and the tool computes the missing term, e.g. 2:3 = 10:15.

Is 3:2 the same as 2:3?

No. Ratios are ordered, so 3:2 and 2:3 describe different proportions even though both are already in lowest terms.

Are my numbers sent anywhere?

No. Everything is computed in your browser; nothing is uploaded.

Sources & references

External references open in a new tab. We are independent and not affiliated with these organizations.

  • ✓ Free to use
  • ✓ No sign-up required
  • ✓ Runs entirely in your browser — nothing is uploaded.
  • ✓ Formula and method shown above
Last updated: How we calculateReport a correctionDisclaimer

Provided “as is” for general information only — results may be inaccurate, so verify before you rely on them. No warranty; use at your own risk.

Built and reviewed by HIFreeTools against the formula shown above and any authoritative references cited on this page. See our methodology and editorial standards.

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