What this calculator does
Scaling keeps the shape of a ratio and changes its size. Multiplying 2 : 3 by 5 gives 10 : 15, which is the same relationship in bigger numbers. This is how you turn a recipe for 2 into a recipe for 10.
How to use it
- Type the ratio you start with.
- Enter a scale factor, for example 2.5, or the value the first part should become.
- Press Scale it.
The method
Multiply every part by the same factor. If you gave a target for the first part, the factor is target ÷ first part.
2 : 3 × 2.5 = 5 : 7.5
Target 10 for the first part: factor = 102 = 5, so 2 : 3 becomes 10 : 15
Examples you can try
| Ratio | Scale | Result |
|---|---|---|
| 2 : 3 | × 2.5 | 5 : 7.5 |
| 1 : 4 | × 10 | 10 : 40 |
| 3 : 5 | first part becomes 12 | 12 : 20 |
| 4 : 6 : 8 | × 0.5 | 2 : 3 : 4 |
Where people use it
- Recipes: a drink with 2 cups concentrate to 3 cups water, scaled so you use 10 cups of concentrate, needs 15 cups of water.
- Models and maps: scale a drawing up or down while keeping proportions.
- Mixes and doses: scale a mix to the batch size you actually need.
Tips
- A factor above 1 makes the ratio bigger; between 0 and 1 makes it smaller.
- Scaling never changes the ratio. You can always confirm with the simplify calculator.
Want to learn the method?
How to simplify a ratio, step by stepRead our short guide with worked examples you can follow on paper.
Frequently asked questions
What does it mean to scale a ratio?
To multiply every part by the same number so the ratio keeps its shape but changes its size.
How do I scale a ratio to a target number?
Divide the target by the matching part to get the factor, then multiply every part by it.
Can I scale down?
Yes. Use a factor smaller than 1, such as 0.5.
Does scaling change the ratio?
No. 2 : 3 and 10 : 15 are equivalent ratios.
Can I scale a ratio of three numbers?
Yes, up to four parts.