Ratio Calculator

Simplify a ratio to its lowest terms or solve for a missing value in A : B = C : D. See the result as 1 : n, a decimal, and a percentage split. Everything runs in the browser.

Simplify ratios
Solve A : B = C : D
Stays on your device

A ratio compares two quantities. To simplify one, divide both sides by their greatest common factor. To solve an equivalent ratio, cross-multiply: A × D = B × C, then divide to isolate the blank.

Example: a 1920 × 1080 screen is 16 : 9 because both numbers divide by 120. If a recipe calls for 2 cups of flour to 3 cups of water and you use 10 cups of flour, you need (3 × 10) ÷ 2 = 15 cups of water.

Browse the Math hub, solve or check an equation of two ratios with the proportion calculator, find the greatest common factor with the GCF calculator, factor one number with the factoring calculator, work out a share of a total with the percent off calculator and convert units with the mm to inches calculator.

How to use the ratio calculator

Pick Solve A : B = C : D or Simplify a ratio.
To solve, fill in three boxes and leave the unknown one blank.
To simplify, enter the two numbers in the ratio.
Read the answer, plus the 1 : n form, decimal, and percentage split.

Frequently asked questions

What is a ratio calculator?

A ratio calculator compares two quantities. It can reduce a ratio like 1920 : 1080 to its simplest form (16 : 9), or solve a missing value in an equivalent ratio such as 2 : 3 = 10 : ?.

How do I simplify a ratio?

Divide both numbers by their greatest common factor. For 12 : 18 the greatest common factor is 6, so the ratio simplifies to 2 : 3. If the ratio has decimals, multiply both sides by 10 or 100 first to make them whole numbers.

How do I solve A : B = C : D for a missing value?

Cross-multiply. A × D = B × C. To find D, use D = (B × C) ÷ A. For 2 : 3 = 10 : D, D = (3 × 10) ÷ 2 = 15.

What is the difference between a ratio and a proportion?

A ratio compares two numbers, like 2 : 3. A proportion says two ratios are equal, like 2 : 3 = 10 : 15. Solving for a missing term in a proportion is the same as scaling a ratio up or down.

How do I convert a ratio to a percentage?

Add the two parts to get the total, then divide each part by the total and multiply by 100. A 3 : 5 ratio is 3 ÷ 8 = 37.5% and 5 ÷ 8 = 62.5% of the whole.

How do I write a ratio as 1 : n?

Divide both sides by the first number. 4 : 10 becomes 1 : 2.5. This form is handy for scale drawings, mixing instructions, and gear ratios.

Can I use decimals in the ratio calculator?

Yes. Enter decimals such as 1.5 : 2.5 and the calculator scales them to whole numbers before reducing, so 1.5 : 2.5 simplifies to 3 : 5.

Is my information saved or uploaded?

No. The ratio calculator runs entirely in your browser. Numbers are not sent to a server or stored, and there is no account.