Ratio Calculator
Enter values in three of the four fields below. The calculator solves for the missing value to keep the ratio equal.
Fill in any three values. Leave the fourth blank — we'll solve it.
=
Solution
D = 15
How it works
A ratio A : B = C : D means A × D = B × C (cross-multiplication). Solving for any missing term: D = B × C ÷ A; C = A × D ÷ B; A = B × C ÷ D; B = A × D ÷ C.
Frequently asked
- What is the difference between a ratio and a proportion?
- A ratio compares two quantities (3 : 4). A proportion is a statement that two ratios are equal (3 : 4 = 6 : 8). This calculator solves proportions.
- How do I simplify a ratio?
- Divide both sides by their greatest common divisor. 12 : 18 simplifies to 2 : 3 (both divided by 6).
- How do I convert a ratio to a percentage?
- For a ratio A : B, the first part as a percent of the total is A ÷ (A + B) × 100. So 3 : 7 means 30% : 70%.
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