Proportion Calculator
Solve a proportion of the form A is to B as C is to X for the missing value X.
Calculate
Enter your values below.
Result
X (the missing value)
0
Formula used
A ⁄ B = C ⁄ X, so X = (B × C) ÷ A
Example: 2 is to 4 as 3 is to X → X = 6.
How to use this calculator
- Enter A, B, C.
- Press Calculate to see your result instantly.
FAQ
Frequently asked questions
What is a proportion?
A proportion states that two ratios are equal: A/B = C/X.
How do you solve for the missing value?
Cross-multiply and divide: X = (B × C) ÷ A.
Can A be zero?
No — dividing by zero is undefined, so A must be non-zero.
Where are proportions used?
Common uses include scaling recipes, currency conversion, and map scale calculations.