Math
Proportion Calculator
Solve a proportion of the form a over b equals x over d, finding the missing value x.
The value of x is the missing number that keeps both sides of the proportion equal, so the two fractions have the same value when x is used.
Formula
From a ÷ b = x ÷ d, cross-multiplying gives x = (a × d) ÷ b.
How it works
Enter a, b, and d. The calculator cross-multiplies and divides to find the missing value that keeps both fractions equal.
Worked example
For example, with a = 3, b = 4 and d = 20, x = (3 × 20) ÷ 4 = 15, so 3 ÷ 4 equals 15 ÷ 20.
FAQs
What does the Proportion do?
It takes the values you enter and works out the proportion for you, showing the result straight away.
What should I enter?
Enter ordinary numbers in the boxes above. If a value does not make sense for this calculation, the page will ask you to check it instead of showing a wrong answer.
Can I use the result for homework or everyday math?
Yes. It is a general-purpose math helper; for exam or professional work, still check the steps against your own working.
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