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Ratio Calculator

Enter a ratio to reduce it to its lowest terms.

A ratio calculator with two modes. Simplify reduces any ratio like 18:24 to its lowest terms (3:4) using the greatest common divisor. Solve or scale finds the missing value in a proportion such as 2:3 = 10:x, which is also how you scale a recipe, a mix measured in ml or grams, or a map distance to a new amount. Type the numbers and the answer updates instantly, with zero denominators handled safely.

How to use

  1. Pick a mode: Simplify a ratio, or Solve or scale a ratio.
  2. To simplify, enter both whole number terms (for example 18 and 24).
  3. To solve a proportion, enter a, b, and c for a:b = c:x.
  4. To scale a ratio to an amount you already have, enter the ratio as a and b, then your amount as c. The answer x is the matching amount of the other part.
  5. Read the result instantly in the output area below.
  6. Use Copy result to grab the answer, or Reset to clear the fields.

Examples

  • Simplify 18:24, the calculator divides both terms by 6 to give 3:4.
  • Solve 2:3 = 10:x, the answer is x = 15.
  • Solve 4:5 = 3:x, the answer is x = 3.75.
  • Scale a 1:2 mix when you have 300 ml of the first part: solve 1:2 = 300:x, so x = 600 ml of the second part.
  • Brew coffee at a 1:16 ratio of coffee to water with 20 g of coffee: solve 1:16 = 20:x, so x = 320 g of water.

FAQs

What is a ratio?
A ratio compares two quantities by division. 3:4 means that for every 3 of the first thing there are 4 of the second. The same ratio can be written with a colon (3:4), as a fraction (3/4), or in words (3 to 4).
How do you simplify a ratio?
Divide both terms by their greatest common divisor (GCD). For 18:24 the GCD is 6, so the ratio reduces to 3:4. This calculator does that step automatically.
How do you scale a ratio?
Multiply or divide both terms by the same number. Doubling 2:3 gives 4:6, which is the same ratio. To scale to a specific amount, set up a proportion: if a concentrate is mixed 1:4 with water and you have 250 ml of concentrate, solve 1:4 = 250:x to get x = 1,000 ml of water.
What is cross multiplication?
Cross multiplication checks or solves a proportion. Two ratios a:b and c:d are equal when a times d equals b times c. To find a missing fourth value, rearrange it to d = (b times c) divided by a. For 2:3 = 10:x, x = (3 times 10) divided by 2 = 15.
How do you write a ratio as a fraction?
A ratio a:b becomes the fraction a/b, which compares the first part to the second. To show each part as a share of the whole, add the terms: in a 2:3 ratio the first part is 2/5 of the total and the second part is 3/5.
What is a proportion?
A proportion states that two ratios are equal, written a:b = c:x. Given any three values, you can solve for the fourth. Here x is found with x = (b times c) divided by a.
Why can the first term of a proportion not be zero?
Solving a:b = c:x divides by a, so a value of zero would mean dividing by zero, which has no answer. The calculator flags this instead of returning an error value.
Can I simplify a ratio with decimals?
Simplify mode works on whole numbers, since a ratio of counts is reduced using the GCD. If you have decimals, scale both terms to whole numbers first (for example 1.5:2 becomes 3:4).
Does it handle negative numbers?
Yes. In simplify mode a negative ratio is reduced and the sign is kept on the first term, so 6:-9 becomes -2:3.
Are my numbers sent anywhere?
No. All calculations run in your browser. Nothing you type is uploaded or stored.

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