Math Calculator
Proportion Calculator.
Solve a/b = c/d for any missing value. Cross-multiply proportions and check ratios instantly.
a / b = c / d
Solved value (d)
8
Left Ratio (a÷b)0.75
Right Ratio (c÷d)0.75
As Percentage (a/b)75%
Why Use a Proportion Calculator?
Proportions show up in recipes, maps, finance, and homework. This free proportion calculator finds the missing number in a/b = c/d so you can scale recipes, convert units, or check equivalent ratios without doing the algebra by hand.
How to Solve a Proportion
a × d = b × c
Cross-multiply, then isolate the unknown. Example: if a/4 = 6/8, then a = (4 × 6) ÷ 8 = 3.
Frequently Asked Questions (FAQs)
How do you solve a proportion?
For a/b = c/d, cross-multiply: a × d = b × c. Then isolate the unknown. If x/b = c/d, then x = (b × c) / d.
What is the difference between a ratio and a proportion?
A ratio compares two quantities (like 3:4). A proportion states that two ratios are equal (like 3/4 = 6/8).
Can this calculator find any missing value?
Yes. Choose which of a, b, c, or d is unknown and enter the other three — the tool solves via cross-multiplication.