Ratio Calculator
Simplify ratios, solve A:B = C:D and scale a ratio up or down.
Enter your values to see the result.
Continue your work
- Proportion Calculator — Solve any missing value in a proportion.
- GCF & HCF Calculator — Find the common factor used to simplify.
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Clear instructions
Find steps, examples and limitations below.
Use online
Open the tool in a supported web browser.
Free to use
No sign-up required. Tool-specific limits may apply.
How to use the Ratio Calculator
Simplify ratios, solve A:B = C:D and scale a ratio up or down.
- 1 Choose Simplify a ratio or Solve A:B = C:D.
- 2 Enter the ratio, or A, B and C.
- 3 Read the simplified ratio or the value of D.
Example and practical tips
A recipe for 3 people uses 4 cups of flour. For 15 people, solve 3:4 = 15:D to get 20 cups.
Frequently asked questions
How is a ratio simplified?
Every part is divided by their greatest common factor. 12:18:30 divides by 6 to give 2:3:5.
Can a ratio have decimals?
Yes. Decimals are scaled up to whole numbers before simplifying.
Report an issue
Something broken or not quite right? Tell us and we will look into it.