Ratio Calculator

Simplify a ratio to its lowest terms or solve a proportion for a missing value. Free, instant, no sign-up.

Ratio Calculator

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Ratio Calculator Guide

Simplify a ratio to its lowest terms, or solve a proportion to find a missing value. Handy for recipes, scale drawings, mixing, and comparisons.

The Methods

Simplify: divide both sides by their greatest common divisor. Solve A : B = C : D: the missing value D = B × C ÷ A (cross-multiply).

How Do I Simplify a Ratio?

Find the greatest common divisor of both numbers and divide each by it. For 18 : 24, the GCD is 6, so the simplified ratio is 3 : 4.

Examples

TaskResult
Simplify 18 : 243 : 4
Simplify 100 : 405 : 2
Solve 3 : 4 = 9 : ?? = 12

Working with fractions? Use the Fraction Calculator; for percentages, the Percentage Calculator.

Frequently Asked Questions

How do I simplify a ratio?
Divide both numbers by their greatest common divisor — for 18:24, divide by 6 to get 3:4.

How do I solve a proportion?
Cross-multiply: for A:B = C:D, the missing value equals the product of the diagonal known values divided by the remaining one.

What does a ratio mean?
A ratio compares two quantities, showing how much of one there is relative to the other.

How do I convert a ratio to a fraction?
Write the first number over the second — the ratio 3:4 is the fraction 3/4.

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