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Ratio Calculator

Simplify a ratio like 12:18 to lowest terms, find an equivalent ratio, or split an amount according to a ratio, and see what percentage of the total each part represents.

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Calculator

What do you want to do?

Simplified ratio

1 : 2

2 : 4

As a quotient

0.5

A ÷ B

Share of the total

33.33% / 66.67%

A and B out of A + B

A as a percentage of B
50%
1 : x form
1 : 2

Step by step

GCF = 2

Divide both terms by 2: 1 : 2

Keep analyzing

For estimates only. Double-check the numbers before making important decisions.

What a ratio means

A ratio compares two quantities. 2:4 is read "2 to 4" and means that for every 2 of one thing there are 4 of the other. Two ratios are equivalent when they describe the same relationship, like 2:4 and 1:2.

  • Simplify: reduces A:B to its simplest form and shows it as a quotient, as a 1:x ratio and as shares of the total.
  • Equivalent ratio: enter one term of the new ratio and get the missing one, plus the scale factor.
  • Split an amount: divides a total into two parts in the ratio A:B.

How ratios are simplified and scaled

A : B = (A ÷ GCF) : (B ÷ GCF)
Equivalent ratio: A : B = (A × k) : (B × k)
Split: part A = total × A ÷ (A + B)

If a ratio has decimals, both terms are first multiplied by 10, 100 and so on to get whole numbers: 1.5:2.5 becomes 15:25, which simplifies to 3:5.

Ratios and percentages

RatioShare of the totalA as a percent of B
1 : 150% and 50%100%
1 : 233.33% and 66.67%50%
3 : 537.5% and 62.5%60%

Common uses

  • Recipes and mixtures, such as 2 parts water to 1 part concentrate.
  • Splitting costs, profits or work in proportion to what each person put in.
  • Aspect ratios for screens and photos: at 16:9, a width of 1,920 pixels gives a height of 1,080.

Example

Two partners invest $2,000 and $3,000, so their ratio is 2,000:3,000, which simplifies to 2:3. If they split a $1,250 profit in that ratio, the first partner gets $500 and the second gets $750.

  1. GCF(2,000, 3,000) = 1,000
  2. 2,000 ÷ 1,000 : 3,000 ÷ 1,000 = 2 : 3
  3. Total parts = 2 + 3 = 5
  4. 1,250 × 2 ÷ 5 = 500 and 1,250 × 3 ÷ 5 = 750

Common mistakes

  • Reading the terms of a ratio as fractions of the total: in 1:2, the first part is one third of the total, not one half.
  • Adding or subtracting the same number from both terms to get an equivalent ratio: you have to multiply or divide.
  • Writing the terms in the wrong order: 3:5 and 5:3 are different ratios.

Frequently asked questions

How do you simplify a ratio?

Divide both terms by their greatest common factor. For 12:18 the GCF is 6, so the ratio simplifies to 2:3.

What is the difference between a ratio and a proportion?

A ratio compares two quantities (a:b). A proportion is an equation that sets two ratios equal (a/b = c/d), and you use it to find a missing value.

Can you simplify a ratio with decimals?

Yes. Multiply both terms by 10 (or 100) to remove the decimals, then simplify: 1.5:2.5 becomes 15:25, which reduces to 3:5.

How do you split a number by a ratio?

Add the terms to get the total number of parts, divide the amount by that number, then multiply by each term. $100 in a 2:3 ratio is $100 ÷ 5 = $20 per part, so $40 and $60.

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