Ratio Calculator
Simplify a ratio to its lowest terms and solve proportions — enter A : B and a value for C to find the matching D.
How to use it
- Enter the two sides of your ratio in A and B.
- Put a scaled value in C and the matching D is worked out for you.
- The simplified form divides both sides by their greatest common factor.
Examples
| 16 : 9, C = 1920 | D = 1080 |
| 48 : 18 | 8 : 3 |
A ratio compares two quantities by division rather than subtraction — 16 : 9 says the first quantity is 16/9 times the second, whatever units either is measured in. This tool does two related jobs: reducing a ratio to its simplest whole-number form, and solving a proportion, where scaling one side of a known ratio tells you how much the other side should scale by.
Worked example — scaling a recipe
A recipe uses flour to sugar in a 3 : 2 ratio and calls for 300 g of flour. To scale it up to use 500 g of flour, set A : B = 3 : 2 and C = 500: D = 500 × 2 ÷ 3 ≈ 333 g of sugar. The ratio stays fixed; both quantities move together.
Common uses
- Recipe and mixture scaling — concrete, paint, cocktails, cleaning solutions.
- Screen and image aspect ratios — 16:9, 4:3, 21:9.
- Map and drawing scales — 1:50 or 1:25,000.
- Financial ratios such as debt-to-income, expressed the same way.
Questions people ask
How do I simplify a ratio?
Divide both sides by their greatest common factor. 48 : 18 both divide by 6, giving 8 : 3.
Can I use it for aspect ratios?
Yes — put 16 and 9 in A and B, then a screen width in C to get the matching height. The dedicated aspect-ratio calculator adds common presets.
Is anything sent to a server?
No. Every calculation runs in your browser, so nothing you type is uploaded and the page keeps working offline once it has loaded.
Last updated 17 August 2026