UtilityLake
Math & Everyday Calculators

Rule of Three Calculator

Use Rule of Three Calculator free in your browser. No account required; your input is processed locally in your browser.

Runs locallyYour inputs stay in your browser.
Workspace
Result
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HOW IT IS CALCULATED

Solve a proportional rule of three

Given a:b = c:x, UtilityLake calculates the missing fourth value.

Instant resultClear formulaRuns locally
01Values
02x = b × c ÷ a
03Result

2:4 = 3:x → x = 6

GOOD TO KNOW

The rule of three is simply a proportion

Its familiar shortcut comes directly from cross multiplication.

02

In short

What logic does the calculator use?

x = b × c ÷ a

Example?

2:4 = 3:x → x = 6