What is ratio?
A ratio compares two or more quantities and shows how much of one thing there is compared with another.
A ratio is a way of comparing parts. It shows the relationship between two or more numbers, such as 2:1, 3:2 or 4:3:1.
For example, if squash is mixed at a ratio of 1:4, that means 1 part squash to 4 parts water. There are 5 parts in total.
Why ratios matter
Ratios are useful whenever you need to compare, split or scale quantities. They appear in recipes, paint mixes, maps, classroom maths, unit prices, business figures and everyday comparisons.
Ratio formula
To simplify a ratio, divide every part by the same common factor. To scale a ratio, multiply every part by the same number.
Simplified ratio = each part ÷ highest common factorScaled ratio = each part × multiplierIf you are splitting a total into a ratio, add the ratio parts first, divide the total by that number of parts, then multiply each ratio part by the value of one part.
Need to simplify or scale a ratio?
Use the ratio calculator to simplify ratios, scale them up or split a total into parts.
Ratio example
Suppose £100 is split in the ratio 2:3. There are 5 parts in total. Each part is worth £20, so the split is £40 and £60.
| Step | Calculation | Result |
|---|---|---|
| Add parts | 2 + 3 | 5 parts |
| Find one part | £100 ÷ 5 | £20 |
| Apply ratio | 2 × £20 and 3 × £20 | £40 and £60 |
Simplifying ratios
Simplifying a ratio means making the numbers smaller without changing the relationship between them. For example, 10:20 simplifies to 1:2 because both parts can be divided by 10.
10:20 ÷ 10 = 1:2A simplified ratio is easier to read, compare and use in everyday calculations.
Scaling ratios
Scaling a ratio means increasing or decreasing every part by the same multiplier. If a recipe uses a 2:1 ratio and you double it, the scaled ratio becomes 4:2. The relationship is still the same.
This is why ratios are useful for recipe scaling, mixing quantities, sharing totals and comparing prices.
Common uses of ratios
- Scaling recipes up or down.
- Splitting money or quantities into shares.
- Comparing two quantities in simple terms.
- Working with unit prices and value comparisons.
- Understanding proportions, percentages and mixtures.
Ratio FAQs
What does ratio mean?
A ratio compares two or more quantities. For example, 2:3 means 2 parts of one thing for every 3 parts of another.
How do you simplify a ratio?
Divide every part of the ratio by the same common factor until the parts cannot be reduced further.
How do you split a total by a ratio?
Add the ratio parts, divide the total by that number of parts, then multiply each part by the value of one part.
Is a ratio the same as a percentage?
No. A ratio compares parts, while a percentage expresses something out of 100. You can often convert between them, but they are not the same format.