XYCalc

Ratio Calculator

Simplify a ratio, find the missing number in an equal ratio, or share an amount in a ratio such as 2:3:5. With the working shown.

New: please check your results.

Simplest form
3 : 2
Starting from 1
1 : 0.67

What it does

A ratio compares amounts, like 3 parts sand to 1 part cement. Simplify a ratio to its smallest whole numbers, find the missing number when two ratios are equal, or share a total between people or ingredients in a given ratio.

How to use it

What do you want to do?

Choose the sum you need, and the boxes change to match.

Ratio

Two or more numbers separated by colons, such as 12:8 or 2:3:5. Decimals work too (1.5:2.25).

Amount to share

The total to split, such as money, a quantity of ingredients or a number of hours.

A

For a missing number in A : B = C : ?, the first number of the ratio you know.

B

The second number of the ratio you know.

C

The number you know in the second ratio, matching A.

Common uses

  • Mixing mortar, concrete or paint in the right proportions.
  • Scaling a recipe up or down.
  • Splitting a bill, profit or inheritance fairly.
  • Working with fractions. Try the Fractions Calculator

The formula

Simplify: divide every part by their highest common factorMissing number: A : B = C : x, so x = B × C ÷ ASharing: one part = amount ÷ total parts, each share = its part × one part

Where:

Highest common factor
the biggest number that divides every part exactly
Total parts
the parts of the ratio added together (2:3:5 has 10)

Decimal ratios are first multiplied up to whole numbers: 1.5 : 2.25 becomes 150 : 225, which simplifies to 2 : 3.

Worked example

To simplify 12 : 8:

  • The highest common factor of 12 and 8 is 4
  • Divide each part by 4: 3 : 2

As one part to another, that's 1 : 0.67.

Questions people ask

How do I simplify a ratio?

Find the biggest number that divides into every part, then divide each part by it. For 12:8 that's 4, giving 3:2. If no number above 1 divides them all, the ratio is already in its simplest form.

How do I share an amount in a ratio?

Add the parts to get the total number of parts, divide the amount by that total to find one part, then multiply each part of the ratio by it. £300 in the ratio 2:3:5 is 10 parts of £30, so £60, £90 and £150.

Does the order of a ratio matter?

Yes. 3:1 sand to cement is very different from 1:3. Keep the order the same as the things you're comparing.

Last checked 26 October 2026