Ratio Calculator

Reduce a ratio to its simplest form, or share out a total according to a ratio.

Simplify a ratio A : B

Simplified ratio2 : 3
As a fraction
2/3
As a decimal (a ÷ b)
0.6666666667
Share of the total
40% : 60%

Working

  1. Divide both terms by their greatest common factor to get 2 : 3.

Divide a total in a ratio

Separate the terms with colons. Up to 10 terms.

Shares200 : 300
Part 1 (2 of 5 parts)
200
Part 2 (3 of 5 parts)
300

Working

  1. Add the ratio terms: 2 + 3 = 5 parts
  2. One part = 500 ÷ 5 = 100
  3. Multiply each term by the value of one part.

What a ratio tells you

A ratio compares quantities by how many times one contains the other. 2 : 3 means “for every 2 of the first, there are 3 of the second”, so the first is 2/5 of the total and the second is 3/5.

simplify: a : b = (a ÷ g) : (b ÷ g), where g = GCF(a, b)

share of term i = total × termi ÷ (sum of all terms)

Worked examples

Simplify 12 : 18

  1. GCF(12, 18) = 6
  2. 12 ÷ 6 = 2 and 18 ÷ 6 = 3

12 : 18 = 2 : 3

Share 500 in the ratio 2 : 3

  1. Total parts: 2 + 3 = 5
  2. One part: 500 ÷ 5 = 100
  3. Shares: 2 × 100 = 200 and 3 × 100 = 300

500 split 2 : 3 is 200 and 300.

Decimal ratios

Ratios with decimals, like 1.5 : 2.5, are scaled to whole numbers first (15 : 25) and then simplified to 3 : 5.

Everyday uses

  • Mixing concrete, paint, fuel or cleaning solutions (e.g. 1 : 4 concentrate to water).
  • Splitting a shared bill or prize unevenly.
  • Scaling a recipe or a drawing while keeping proportions.
  • Screen shapes such as 16 : 9 aspect ratio.