Proportion Calculator
Solve proportion problems and find missing values in ratios
Enter three known values and select which variable to solve for.
Enter values and click Calculate to see the result
How Proportions Work
In a proportion a/b = c/d, the cross products are equal: a × d = b × c
To find a missing value, we rearrange this equation to solve for the unknown variable.
Understanding Proportions
Proportion
An equation stating that two ratios are equal: a/b = c/d
Cross Products
In a proportion, a × d = b × c (cross multiplication)
Ratios
A comparison of two quantities expressed as a fraction
Applications
Used in scaling, unit conversion, and percentage calculations
Example 1: Recipe Scaling
If 2 cups of flour make 12 cookies, how much flour is needed for 18 cookies?
2/12 = x/18 → x = (2 × 18) ÷ 12 = 3 cups
Example 2: Map Scale
On a map, 1 inch represents 50 miles. How many miles does 3.5 inches represent?
1/50 = 3.5/x → x = (3.5 × 50) ÷ 1 = 175 miles
Related Tools
Standard Calculator
Basic arithmetic calculator for everyday calculations
Average Calculator
Calculate mean, median, mode of numbers
Scientific Calculator
Advanced calculator with scientific functions