Ratio Calculator
The Ratio Calculator solves for the unknown D in the proportion A:B = C:D and simplifies a ratio to its lowest terms — handy for scaling recipes, mixing ratios, and everyday proportion problems.
How to use
- 1Enter values A, B, and C.
- 2See D calculated instantly.
- 3Also see the simplified A:B ratio.
Why FREE PDF?
- Completely free
- No account required
- Processing happens in your browser whenever possible
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Frequently Asked Questions
How is the rule of three (A:B = C:D) solved?
Enter the three known values (A, B, C); the missing fourth value (D) is calculated automatically using the proportion rule.
How do I reduce a ratio to its simplest form?
Enter two numbers, and it finds their common divisor to show the ratio in its smallest whole-number form (e.g. 8:12 → 2:3).
When is this tool useful?
It's useful for scaling recipes, mixture ratios, or proportional calculations like map scale.
Does it work with decimal numbers?
Yes, besides whole numbers, you can also do proportion calculations with decimal values.