Ratio & Proportion Calculator
Solve proportions A : B = C : X and simplify ratios.
How to use the Ratio & Proportion Calculator
Useful for recipes, scale drawings, mixing and currency.
Formula
X = B × C ÷ A
Worked example
3 : 4 = 15 : X gives X = 20.
Frequently asked questions
How do I scale a recipe?
Treat the original and new servings as a ratio and multiply every ingredient by new ÷ original.
Results are estimates for educational and planning purposes. Always confirm important financial, health or legal decisions with a qualified professional. Last reviewed 2026-09-27.